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OPTIMISATION OF STEAM TURBINE BLADE MATERIAL amp ITS ANALYSIS
A project report submitted to
Jawaharlal Nehru Technological University
Kakinada in the partial fulfillment for the award of
Degree of BACHELOR
OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
Submitted by
VSURENDRA KUMAR
GCALEB PAUL ARAHUL
MLOKESH GSIVA
Under the esteemed guidance of
MrKCHANDRA SEKHARAsso Professor
BATCH 2009-13 DEPARTMENT OF MECHANICAL ENGINEERING
QISCOLLEGE OF ENGINEERING amp TECHNOLOGY
An ISO Certified amp accredited by NBA institute (Affiliated to JawaharlalNehruTechnologicalUniversity Kakinada)
ONGOLE ndash 523 272 AP
QISCOLLEGE OF ENGINEERING amp TECHNOLOGY
An ISO Certified amp accredited by NBA institute (Affiliated to JawaharlalNehruTechnologicalUniversity Kakinada)
VENGAMUKKA PALEM ndash 523272 AP
DEPARTMENT OF MECHANICAL ENGINEERINGCERTIFICATE
This is to certify that the project entitled
ldquoOPTIMIZATION OF STEAM TURBINE BLADE MATERIAL amp ITS
ANALYSISrdquois a bonafied work of the following final BTech studentsin
the partial fulfillment of the requirement for the award of the degree of
Bachelor of Technology inMECHANICAL ENGINEERING
for the academic year 2009-13
VSURENDRA KUMAR
GCALEB PAUL ARAHUL
MLOKESH GSIVA
Signature of guide Signature of Head of DepartmentMrKCHANDRASEKHAR Dr BSRMURTHY MTech( PhD) MTechPhD
Signature of Principal Signature of External Examiner DrKVEERASWAMY ME PhD
DECLARATION
We do here by declare that the project report entitled
ldquoOPTIMISATION OF STEAM TURBINE BLADE
MATERIAL amp ITS ANALYSISrdquo is an original work done and
submitted by us as a partial fulfillment for the award of degree of
Bachelor of Technology
Date
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ACKNOWLEDGEMENT
We thank the almighty for giving us the courage and perseverance in completing
the project This is itself an acknowledgement for all those people who have given us
their heartfelt cooperation in making this project a grand success
It is great pleasure to express our deep and sincere gratitude to the project guide
SriKCHANDRA SEKHAR MTech(PhD) Associate professor for extending their
sincere and heart full guidance throughout the project work
We are greatly debated to our Head of the deptDrBVSMURTHY MTECH
PhDfor giving valuable guidance at every stage of the project work We are profoundly
grateful towards the unmatched services rendered by himWe are thankful to our
principal DrKVEERASWAMY ME PhD MISTE for giving us the opportunity for doing
this project at an esteemed organization
Our special thanks to all lectures of Mechanical Engineering department for their
valuable advices at every stage of this work Without their supervision and many hours of
devoted guidance stimulating and constructive criticism and this thesis would never
have come out in this form
We would like to thank our friends whose direct or indirect help has enabled us to
complete this work successfully
Last but not least we would like to express our deep sense of gratitude to our
beloved parents for their moral support
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ABSTRACT
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam and converts it into rotary motion A system of angled and shaped blades arranged
on a rotor through which steam is passed to generate rotational energy
The blades are designed in such a way as to produce maximum rotational energy by
directing the flow of the steam along its surface The blades are made at specific angles in
order to incorporate the net flow of steam over it in its favor The blades may be of
stationary or fixed and rotary or moving or types
The main aim of the project is to suggest the best material with in low cost The
project equipped with the construction and analysis of steam turbine blade with different
materials used generally (chrome steel titanium) and the project improves the mechanical
properties like stress displacement temperature gradient and thermal flux etc of
bladematerial for which the new material usage is introduced which is cast iron with
zirconium coating
The theme of the project is to design a steam turbine blade using 3D modeling
software ProEngineer by using the CMM point data
In this project we are conducting structural and modal analysis by applying the
pressures By conducting above analysis we are finding stresses developing on blade and
mode shape of the blade In our project we are also conducting thermal analysis for
finding temperature distributing on blade
ProENGINEER is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design
Thermal analysis to verify the thermal characteristics of the blade is also done by
applying temperatures Structural and thermal analyses are done in ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
An ISO Certified amp accredited by NBA institute (Affiliated to JawaharlalNehruTechnologicalUniversity Kakinada)
ONGOLE ndash 523 272 AP
QISCOLLEGE OF ENGINEERING amp TECHNOLOGY
An ISO Certified amp accredited by NBA institute (Affiliated to JawaharlalNehruTechnologicalUniversity Kakinada)
VENGAMUKKA PALEM ndash 523272 AP
DEPARTMENT OF MECHANICAL ENGINEERINGCERTIFICATE
This is to certify that the project entitled
ldquoOPTIMIZATION OF STEAM TURBINE BLADE MATERIAL amp ITS
ANALYSISrdquois a bonafied work of the following final BTech studentsin
the partial fulfillment of the requirement for the award of the degree of
Bachelor of Technology inMECHANICAL ENGINEERING
for the academic year 2009-13
VSURENDRA KUMAR
GCALEB PAUL ARAHUL
MLOKESH GSIVA
Signature of guide Signature of Head of DepartmentMrKCHANDRASEKHAR Dr BSRMURTHY MTech( PhD) MTechPhD
Signature of Principal Signature of External Examiner DrKVEERASWAMY ME PhD
DECLARATION
We do here by declare that the project report entitled
ldquoOPTIMISATION OF STEAM TURBINE BLADE
MATERIAL amp ITS ANALYSISrdquo is an original work done and
submitted by us as a partial fulfillment for the award of degree of
Bachelor of Technology
Date
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ACKNOWLEDGEMENT
We thank the almighty for giving us the courage and perseverance in completing
the project This is itself an acknowledgement for all those people who have given us
their heartfelt cooperation in making this project a grand success
It is great pleasure to express our deep and sincere gratitude to the project guide
SriKCHANDRA SEKHAR MTech(PhD) Associate professor for extending their
sincere and heart full guidance throughout the project work
We are greatly debated to our Head of the deptDrBVSMURTHY MTECH
PhDfor giving valuable guidance at every stage of the project work We are profoundly
grateful towards the unmatched services rendered by himWe are thankful to our
principal DrKVEERASWAMY ME PhD MISTE for giving us the opportunity for doing
this project at an esteemed organization
Our special thanks to all lectures of Mechanical Engineering department for their
valuable advices at every stage of this work Without their supervision and many hours of
devoted guidance stimulating and constructive criticism and this thesis would never
have come out in this form
We would like to thank our friends whose direct or indirect help has enabled us to
complete this work successfully
Last but not least we would like to express our deep sense of gratitude to our
beloved parents for their moral support
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ABSTRACT
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam and converts it into rotary motion A system of angled and shaped blades arranged
on a rotor through which steam is passed to generate rotational energy
The blades are designed in such a way as to produce maximum rotational energy by
directing the flow of the steam along its surface The blades are made at specific angles in
order to incorporate the net flow of steam over it in its favor The blades may be of
stationary or fixed and rotary or moving or types
The main aim of the project is to suggest the best material with in low cost The
project equipped with the construction and analysis of steam turbine blade with different
materials used generally (chrome steel titanium) and the project improves the mechanical
properties like stress displacement temperature gradient and thermal flux etc of
bladematerial for which the new material usage is introduced which is cast iron with
zirconium coating
The theme of the project is to design a steam turbine blade using 3D modeling
software ProEngineer by using the CMM point data
In this project we are conducting structural and modal analysis by applying the
pressures By conducting above analysis we are finding stresses developing on blade and
mode shape of the blade In our project we are also conducting thermal analysis for
finding temperature distributing on blade
ProENGINEER is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design
Thermal analysis to verify the thermal characteristics of the blade is also done by
applying temperatures Structural and thermal analyses are done in ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Signature of Principal Signature of External Examiner DrKVEERASWAMY ME PhD
DECLARATION
We do here by declare that the project report entitled
ldquoOPTIMISATION OF STEAM TURBINE BLADE
MATERIAL amp ITS ANALYSISrdquo is an original work done and
submitted by us as a partial fulfillment for the award of degree of
Bachelor of Technology
Date
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ACKNOWLEDGEMENT
We thank the almighty for giving us the courage and perseverance in completing
the project This is itself an acknowledgement for all those people who have given us
their heartfelt cooperation in making this project a grand success
It is great pleasure to express our deep and sincere gratitude to the project guide
SriKCHANDRA SEKHAR MTech(PhD) Associate professor for extending their
sincere and heart full guidance throughout the project work
We are greatly debated to our Head of the deptDrBVSMURTHY MTECH
PhDfor giving valuable guidance at every stage of the project work We are profoundly
grateful towards the unmatched services rendered by himWe are thankful to our
principal DrKVEERASWAMY ME PhD MISTE for giving us the opportunity for doing
this project at an esteemed organization
Our special thanks to all lectures of Mechanical Engineering department for their
valuable advices at every stage of this work Without their supervision and many hours of
devoted guidance stimulating and constructive criticism and this thesis would never
have come out in this form
We would like to thank our friends whose direct or indirect help has enabled us to
complete this work successfully
Last but not least we would like to express our deep sense of gratitude to our
beloved parents for their moral support
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ABSTRACT
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam and converts it into rotary motion A system of angled and shaped blades arranged
on a rotor through which steam is passed to generate rotational energy
The blades are designed in such a way as to produce maximum rotational energy by
directing the flow of the steam along its surface The blades are made at specific angles in
order to incorporate the net flow of steam over it in its favor The blades may be of
stationary or fixed and rotary or moving or types
The main aim of the project is to suggest the best material with in low cost The
project equipped with the construction and analysis of steam turbine blade with different
materials used generally (chrome steel titanium) and the project improves the mechanical
properties like stress displacement temperature gradient and thermal flux etc of
bladematerial for which the new material usage is introduced which is cast iron with
zirconium coating
The theme of the project is to design a steam turbine blade using 3D modeling
software ProEngineer by using the CMM point data
In this project we are conducting structural and modal analysis by applying the
pressures By conducting above analysis we are finding stresses developing on blade and
mode shape of the blade In our project we are also conducting thermal analysis for
finding temperature distributing on blade
ProENGINEER is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design
Thermal analysis to verify the thermal characteristics of the blade is also done by
applying temperatures Structural and thermal analyses are done in ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
ACKNOWLEDGEMENT
We thank the almighty for giving us the courage and perseverance in completing
the project This is itself an acknowledgement for all those people who have given us
their heartfelt cooperation in making this project a grand success
It is great pleasure to express our deep and sincere gratitude to the project guide
SriKCHANDRA SEKHAR MTech(PhD) Associate professor for extending their
sincere and heart full guidance throughout the project work
We are greatly debated to our Head of the deptDrBVSMURTHY MTECH
PhDfor giving valuable guidance at every stage of the project work We are profoundly
grateful towards the unmatched services rendered by himWe are thankful to our
principal DrKVEERASWAMY ME PhD MISTE for giving us the opportunity for doing
this project at an esteemed organization
Our special thanks to all lectures of Mechanical Engineering department for their
valuable advices at every stage of this work Without their supervision and many hours of
devoted guidance stimulating and constructive criticism and this thesis would never
have come out in this form
We would like to thank our friends whose direct or indirect help has enabled us to
complete this work successfully
Last but not least we would like to express our deep sense of gratitude to our
beloved parents for their moral support
VSURENDRA KUMARGCALEB PAUL
ARAHULMLOKESH
GSIVA
ABSTRACT
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam and converts it into rotary motion A system of angled and shaped blades arranged
on a rotor through which steam is passed to generate rotational energy
The blades are designed in such a way as to produce maximum rotational energy by
directing the flow of the steam along its surface The blades are made at specific angles in
order to incorporate the net flow of steam over it in its favor The blades may be of
stationary or fixed and rotary or moving or types
The main aim of the project is to suggest the best material with in low cost The
project equipped with the construction and analysis of steam turbine blade with different
materials used generally (chrome steel titanium) and the project improves the mechanical
properties like stress displacement temperature gradient and thermal flux etc of
bladematerial for which the new material usage is introduced which is cast iron with
zirconium coating
The theme of the project is to design a steam turbine blade using 3D modeling
software ProEngineer by using the CMM point data
In this project we are conducting structural and modal analysis by applying the
pressures By conducting above analysis we are finding stresses developing on blade and
mode shape of the blade In our project we are also conducting thermal analysis for
finding temperature distributing on blade
ProENGINEER is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design
Thermal analysis to verify the thermal characteristics of the blade is also done by
applying temperatures Structural and thermal analyses are done in ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
ABSTRACT
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam and converts it into rotary motion A system of angled and shaped blades arranged
on a rotor through which steam is passed to generate rotational energy
The blades are designed in such a way as to produce maximum rotational energy by
directing the flow of the steam along its surface The blades are made at specific angles in
order to incorporate the net flow of steam over it in its favor The blades may be of
stationary or fixed and rotary or moving or types
The main aim of the project is to suggest the best material with in low cost The
project equipped with the construction and analysis of steam turbine blade with different
materials used generally (chrome steel titanium) and the project improves the mechanical
properties like stress displacement temperature gradient and thermal flux etc of
bladematerial for which the new material usage is introduced which is cast iron with
zirconium coating
The theme of the project is to design a steam turbine blade using 3D modeling
software ProEngineer by using the CMM point data
In this project we are conducting structural and modal analysis by applying the
pressures By conducting above analysis we are finding stresses developing on blade and
mode shape of the blade In our project we are also conducting thermal analysis for
finding temperature distributing on blade
ProENGINEER is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design
Thermal analysis to verify the thermal characteristics of the blade is also done by
applying temperatures Structural and thermal analyses are done in ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements
CONTENTS-
CHAPTER-1 INTRODUCTIONTO STEAM TURBINE BLADE
11 INTRODUCTION
12 MANFACTURING OF STEAM TURBINE BLADE
13 OPTIMIZATION TECHNIQUES AND SELECTION
CHAPTER-2 INTRODUCTION TO NEW BLADE MATERIAL
CONCEPT
21 MATERIALS USED TO MANFACTURE STEAM TURBINE BLADE
22 NEW BLADE MATERIAL INTRODUCTION AND ITS PROPERTIES
CHAPTER-3 DESIGN OVERVIEW
31CMM DATA
311GENERATION OF PRESSURE DISTRIBUTION ON TURBINE BLADE
32 LAYER OVERVIEW
33 INTRODUCTION TO CAD
34INTRODUCTION TO PRO-E
35DESIGN OF BLADE
351 DESIGN CONSIDERATIONS
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
352 DESIGN PROCEDURE
CHAPTER-4 ANALYSIS OF STEAM TURBINE BLADE
41INTRODUCTION TO ANSYS
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
CHAPTER-5 RESULTS OF ANALYSIS ON BLADE
CHAPTER-6 CONCLUSION
CHAPTER-7 BIBLIOGRAPHY
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CHAPTER-1INTRODUCTION
TO STEAM TURBINEBLADE
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
11 INTRODUCTION
STEAM TURBINE-
A steam turbine is a mechanical device that extracts thermal energy
from pressurized steam and converts it into rotary motion A system of angled and
shaped blades arranged on a rotor through which steam is passed to generate rotational
energy and this energy is used for generation of power
BLADE-
The blade is one of the crucial part of the Entire turbine construction if the profile is vary
a little bit its entire system efficiency will effects not only blade profile but also the
material used
The blades are of two types Which is stationary blades moving bladesThe stationary
blades are used like nozzles for converting pressure energy into kinetic energy Generally
these are fixed on frame where as the other type of blades are (moving blades) fixed on
rotor these will absorbs energy which is generated from fixed blades This is the
mechanism occurred in the reaction turbine
But where as in impulse turbine the steam (jet) will directly touches the
blade profile here we are going to use of fixed blades In those two types each having
their special features advantages amp disadvantages
The blades are manufactured by using various machining process amp various tools
based on work material (work piece) optimization of tool usage Of course it is a costly
process amp takes more time for reducing both cost amp time we are going to do this project
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Not only that but also we can reduce monthly maintenance like replacement turbine
blades
Generally now a dayrsquos titanium is used as blade material but it is a costly one
so with good properties which are required for blade here our project deals with
optimization of materials with the replacement of titanium with low cost material by use
of refectories It is used like a painting on surface
12 MANUFACTURING OF STEAM TURBINE BLADE
The different processes followed in the manufacture of steam turbine blade on CNC 3axis
machine as follows
1 RAW MATERIAL PROCUREMENTThe steam turbine blade material is procured as
per the design specification The material is inspected dimensionally and all the
mechanical and chemical analysis are made as per the specification
2 LENGTH CUTTING
The material is cut to length by keeping machining allowance at both ends either by Band
Saw or by Power Hack Saw
3 THICKNESS MILLING
The material is clamped in a vice or fixture and thickness is milled on both sides by
keeping n allowance of 05mm on both sides for grinding This operation is done either
by horizontal milling machining or by vertical milling machine
4 THICKNESS GRINDINGThe milled bars are deburred and kept on a magnetic chuck
of the segmental surface grinding machine 5 to 10 blades are kept each time depending
on the size and ground each side to maintain the dimension The tolerance on the grinding
dimensions would be +‐005 mm and parallarith should be within 002 mm
5 RHOMBOID MILLINGThe ground blade bars are milled to rhomboid shape with an
angle given in the process by clamping in a fixture on both sides with an allowance of
05mm on both side This is done on the horizontal milling machines
6 RHOMBOID GRINDING
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
The milled bars are deburred and kept on magnetic chuck of the surface grinder and
grinding is done on both sides and the tolerance should be +‐005 mm The surface must
be within 8 microns
7 FACING AND SIZE MILLING
The ground blades are faced on the root side to maintain perpendicularity This is very
important as the blade is held on this face while in assembly Then on other side size
milling is done to maintain the total length of blades as per the drawing
8 ROOT MILLINGClamp the blade in a vice or ficture and machine the root on both
sides as per drawing keeping an allowance for root radius Do not machine 2 blade as
these are used for locking purpose This operation is done on horizontal milling machine
9 ROOT RADIUS MILLING
Clamp the blade in a vice or fixture and machine the root radius as per drawing by CNC
Machining centre This operation is done on CNC Vertical machining centre by CNC
Program
10 WIDTH MILLINGThe profile width is done on both sides on horizontal milling
machine as per the drawing
11 CONVEX MILLINGThe milling is done on convex side by aCNC machining centre
The CNC Program is developed based on the profile coordinates and then loaded into the
CNC system of the machine
12 CONCAVE MILLING
The profile milling is done on concave side by a CNC machining center The CNC
Program is developed based on the profile coordinate and then loaded in to the CNC
system of the machine
13 TAPER MILLING
The taper milling is done on a horizontal milling machine by putting in a fixture specially made The taper is calculated
Etc are the steps in manufacturing
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
13 OPTIMIZATION TECHNIQUES AND SELECTION
Optimization techniques can be classified based on the type of constraints nature of
design variables physical structure of the problem nature of the equations involved
deterministic nature of the variables permissible value of the design variables
separability of the functionsand number of objective functions
Classification based on the nature of the design variables
1048698There are two broad categories of classification within this classification
1048698First category the objective is to find a set of design parameters that make a prescribed function of these parameters minimum or maximum subject to certain constraints
1048698Second category the objective is to find a set of design parameters which are all continuous functions of some other parameter that minimizes an objective function subject to a set of constraints
Classification based on the physical structure of the problem
1048698Based on the physical structure we can classify optimization problems are classified as optimal controland non-optimal controlproblems
(i)Anoptimal control (OC)problem is a mathematical programming problem involving a number of stages where each stage evolves from the preceding stage in a prescribed manner
1048698It is defined by two types of variables the control or design variables and state variables(ii) The problems which are not optimal control problemsarecalled non-optimal control problems
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Classification based on the nature of the equations involved
1048698Based on the nature of expressions for the objective function and the constraints optimization problems can be classified as linear nonlinear geometric and quadratic programming problems
(i)Linear programming problem1048698If the objective function and all the constraints are linear functions of the design variables the mathematical programming problem is called a linear programming (LP) problem
(ii) Nonlinear programming problem1048698If any of the functions among the objectives and constraint functions is nonlinear the problem is called a nonlinear programming (NLP) problem this is the most general form of a programming problem
(iii)Geometric programming problemndashA geometric programming (GMP) problem is one in which the objective function and constraints are expressed as polynomials in X
(iv) Quadratic programming problem1048698A quadratic programming problem is the best behaved nonlinear programming problem with a quadratic objective function and linear constraints and is concave (for maximization problems)
Classification based on the permissible values of the decision variables
1048698Under this classification problems can be classified asintegerand real-valuedprogramming problems
(i) Integer programming problem1048698If some or all of the design variables of an optimization problem are restricted to take only integer (or discrete) values the problem is called an integer programming problem
(ii) Real-valued programming problem1048698A real-valued problem is that in which it is sought to minimize or maximize a real function by systematically choosing the values of real variables from within an allowed set When the allowed set contains only real values it is called a real-valued programming problem
1048698Under this classification optimization problems can be classified as deterministicandstochastic programming problems
(i) Deterministic programming problem
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
bullIn this type of problems all the design variables are deterministic
(ii) Stochastic programming problem1048698In this type of an optimization problem some or all the parameters (design variables andor pre-assigned parameters) are probabilistic (non deterministic or stochastic) For example estimates of life span of structures which have probabilistic inputs of the concrete strength and load capacity A deterministic value of the life-span is non-attainable
Classification based on the number of objective functions
1048698Under this classification objective functions can be classified as singleand
multiobjectiveprogramming problems
(i)Single-objective programming problemin which there is only a single objective
(ii) Multi-objective programming problem
Optimization Technique Selection Criteria
We have selected the optimization of design variable of material selection criteria
where it can give good results in optimization analysis This technique comes under the
category of optimization under based upon design variables
In the project the total description contains not only optimization and the
comparison of the new material with generally used materials The individual analysis
also done in the total project
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CHAPTER-2INTRODUCTIONTO NEW BLADE
DESIGN
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
21 MATERIALS USED TO MANFACTURE STEAM TURBINE
BLADE
The type of material used for turbine blades is based on the stage of the turbine in
which the blades will operate There are three such stages high-pressure (HP)
intermediate-pressure (IP) and low-pressure (LP) which are named according to the
relative pressure of the steam in the stage The pressures and temperatures of each stage
limit the kinds of materials that may be used in them For instance HP and IP stage
blades are generally made from 12Cr martesitic stainless steels However blades used in
high-temperature (gt 450 C) HP or IP applications may be made of austenitic stainless
steels because they have better mechanical properties at high temperatures For example
stainless steel type AISI 422 (a martensitic stainless steel) is commonly used for HP and
IP turbine sections while AISI series 300 steels (austenitic) are used for high-temperature
applications LP blades are often but not exclusively made from 12Cr stainless steels
also Common types of stainless steel used in LP sections include AISI types 403 410
410-Cb and 630 the exact type of steel chosen for a particular LP application depends
on the strength and corrosion resistance required
Since the 1960s titanium alloys especially Ti-6Al-4V have also been used for
LP turbine stages These alloys are particularly suited to LP stages for a number of
reasons First the densities of titanium alloys are generally less than the density of steels
for example Ti-6Al-4V has a density of only 443 gcc while stainless steel type AISI
410S has a density of 78 gcc This lower density makes it possible to lengthen the LP
blades and thereby increase turbine efficiency without increasing stresses in the blades
due to centrifugal forces Second titanium alloys have greater corrosion resistance than
steels this makes titanium alloys ideal for use in LP stages where there are greater levels
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
of moisture Finally titanium alloys are resistant enough to water droplet erosion that
they can be used without erosion protection in certain applications
Overall it is the material properties that make a blade reliable or doomed to
failure The yield strength tensile strength corrosion resistance and modulus of
elasticity all play a role in determining whether or not a blade will fail under operating
loads
22 NEW BLADE MATERIAL INTRODUCTION AND ITS
PROPERTIES
Generally the blade will be manufactured with stainless steel chrome steel and
some other alloy steels If the higher performance and higher efficiency is needed the
blades are manufactured with titanium which is high in cost and have good properties
Due to high cost it is very difficult to maintain and the initial investment will be high So
a material need is came in front to minimize cost and to proportionate the good properties
in it We selected cast iron with zirconium coating which will give the better properties
than the titanium material The properties of the material are listed below
Cast Iron
Material Metal Ferrous Metal Cast Iron
Material Notes This property data is a summary of similar materials in the MatWeb database for the category Cast Iron Each property range of values reported is minimum and maximum values of appropriate MatWeb entries The comments report the average value and number of data points used to calculate the average The values are not necessarily typical of any specific grade especially less common values and those that can be most affected by additives or processing methods
Physical Properties
Metric English Comments
Density 554 - 781 gcc
0200 - 0282
lbinAcircsup3
Average value 724 gcc Grade Count69
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Mechanical Properties
Metric English Comments
Hardness Brinell
120 - 807 120 - 807 Average value 300 Grade Count134
Hardness Knoop
162 - 906 162 - 906 Average value 288 Grade Count78
Hardness Rockwell B
400 - 970 400 - 970 Average value 693 Grade Count4
Hardness Rockwell C
114 - 650 114 - 650 Average value 292 Grade Count44
Hardness Vickers
151 - 871 151 - 871 Average value 273 Grade Count78
Tensile Strength Ultimate
118 - 1650 MPa
17100 - 240000 psi
Average value 516 MPa Grade Count137
Tensile Strength Yield
655 - 1450 MPa
9500 - 210000 psi
Average value 432 MPa Grade Count104
Elongation at Break
100 - 250 100 - 250
Average value 828 Grade Count93
Reduction of Area
200 - 100 200 - 100
Average value 538 Grade Count13
Modulus of Elasticity
621 - 240 GPa 9000 - 34800 ksi
Average value 147 GPa Grade Count62
Flexural Yield Strength
248 - 655 MPa 36000 - 95000 psi
Average value 515 MPa Grade Count8
Compressive Yield Strength
331 - 2520 MPa
48000 - 365000 psi
Average value 1080 MPa Grade Count28
Poissons Ratio
0240 - 0370 0240 - 0370
Average value 0287 Grade Count36
Fatigue Strength
689 - 510 MPa
10000 - 74000 psi
Average value 260 MPa Grade Count31
Fracture Toughness
440 - 109 MPa-mAcircfrac12
400 - 992 ksi-inAcircfrac12
Average value 700 MPa-mAcircfrac12 Grade Count5
Machinability
0000 - 125 0000 - 125
Average value 390 Grade Count10
Shear Modulus
270 - 676 GPa
3920 - 9800 ksi
Average value 581 GPa Grade Count33
Shear Strength
149 - 1480 MPa
21600 - 215000 psi
Average value 571 MPa Grade Count26
Izod Impact Unnotched
400 - 244 J 295 - 180 ft-lb
Average value 655 J Grade Count12
Charpy 678 - 271 J 500 - 200 Average value 129 J Grade Count9
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Impact ft-lbCharpy Impact Unnotched
407 - 123 J 300 - 910 ft-lb
Average value 703 J Grade Count18
Electrical Properties
Metric English Comments
Electrical Resistivity
000000500 - 110 ohm-cm
000000500 - 110
ohm-cm
Average value 611 ohm-cm Grade Count18
Magnetic Permeability
100 - 750 100 - 750 Average value 410 Grade Count5
Thermal
PropertiesMetric English Comments
CTE linear 775 - 193 Acircmicromm-AcircdegC
431 - 107 Acircmicroinin-
AcircdegF
Average value 127 Acircmicromm-AcircdegC Grade Count29
Specific Heat Capacity
0506 Jg-AcircdegC 0121 BTUlb-
AcircdegF
Average value 0506 Jg-AcircdegC Grade Count6
Thermal Conductivity
113 - 533 Wm-K
784 - 370 BTU-inhr-
ftAcircsup2-AcircdegF
Average value 252 Wm-K Grade Count23
Melting Point
1120 - 2220 AcircdegC
2050 - 4030 AcircdegF
Average value 1210 AcircdegC Grade Count8
Maximum Service Temperature Air
649 - 982 AcircdegC 1200 - 1800 AcircdegF
Average value 720 AcircdegC Grade Count9
Minimum Service Temperature Air
-594 - -300 AcircdegC
-750 - -220 AcircdegF
Average value -349 AcircdegC Grade Count6
Shrinkage 0800 - 150 0800 - 150
Average value 119 Grade Count10
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Zirconium Zr
Material Metal Nonferrous Metal Zirconium Alloy Pure Element
Material Notes This entry is for pure Zr MatWeb also has data sheets for many Zr alloys
Characteristics
DuctileMechanical Properties similar to titanium and austenitic stainless steelExcellent corrosion resistanceTransparent to thermal energy neutronsForms adherent refractory double-oxide layer above 650AcircdegCHighly anisotropic undergoes allotropic transormation from hcp-structured alpha phase to bcc-structured beta phase at 870AcircdegC
Applications
SuperalloysAlloying with Aluminium Copper Magnesium or Titanium
Water-cooled Nuclear reactorsChemical processing equipment
Physical
PropertiesMetric English Comments
Density 653 gcc 0236 lbinAcircsup3 Vapor Pressure 1013e-10 bar 7598e-8 torr
Temperature 1574 AcircdegC Temperature 2865 AcircdegF
1013e-9 bar 7598e-7 torr Temperature 1690 AcircdegC Temperature
3070 AcircdegF 1013e-8 bar 0000007598 torr
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Temperature 1822 AcircdegC Temperature 3312 AcircdegF
1013e-7 bar 000007598 torr Temperature 1976 AcircdegC Temperature
3589 AcircdegF 0000001013 bar 00007598 torr
Temperature 2156 AcircdegC Temperature 3913 AcircdegF
000001013 bar 0007598 torr Temperature 2367 AcircdegC Temperature
4293 AcircdegF 00001013 bar 007598 torr
Temperature 2620 AcircdegC Temperature 4750 AcircdegF
0001013 bar 07598 torr Temperature 2926 AcircdegC Temperature
5299 AcircdegF 001013 bar 7598 torr
Temperature 3304 AcircdegC Temperature 5979 AcircdegF
01013 bar 7598 torr Temperature 3783 AcircdegC Temperature
6841 AcircdegF 1013 bar 7598 torr
Temperature 4409 AcircdegC Temperature 7968 AcircdegF
Chemical Properties
Metric English Comments
Atomic Number 40 40 Thermal Neutron Cross Section
018 barnsatom 018 barnsatom
X-ray Absorption Edge
068877 Atildehellip 068877 Atildehellip K
48938 Atildehellip 48938 Atildehellip LI
537088 Atildehellip 537088 Atildehellip LII
557374 Atildehellip 557374 Atildehellip LIII
Electronegativity 133 133 PaulingIonic Radius 0790 Atildehellip 0790 Atildehellip Crystal Ionic
Radius for Valence +4
109 Atildehellip 109 Atildehellip Crystal Ionic Radius for
Valence +1Electrochemical 0844 gAh 0844 gAh
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Equivalent
Mechanical Properties
Metric English Comments
Hardness Brinell 145 145 Converted from Vickers for 3000
kg load10 mm ball Annealed
sampleHardness Rockwell A
49 49 Converted from Vickers
annealed sampleHardness Rockwell B
78 78 Converted from Vickers
Annealed sampleHardness Vickers 150 150 annealed sampleTensile Strength Ultimate
330 MPa 47900 psi Annealed
Tensile Strength Yield
230 MPa 33400 psi Annealed
Elongation at Break 32 32 AnnealedModulus of Elasticity
945 GPa 13700 ksi
Poissons Ratio 034 034 Shear Modulus 353 GPa 5120 ksi Calculated
Electrical Properties
Metric English Comments
Electrical Resistivity
00000400 ohm-cm 00000400 ohm-cm
Magnetic Susceptibility
000000134 000000134 cgsg
Critical Magnetic Field Strength Oersted
47 47
Critical Superconducting Temperature
0610 K 0610 K Acircplusmn015 065 095 K for omega Zr
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Thermal Properties
Metric English Comments
Heat of Fusion 251 Jg 108 BTUlb CTE linear 580 Acircmicromm-AcircdegC 322 Acircmicroinin-AcircdegF
Temperature 200 - 100 AcircdegC
Temperature 680 - 212 AcircdegF
630 Acircmicromm-AcircdegC 350 Acircmicroinin-AcircdegF Temperature 250 AcircdegC Temperature
482 AcircdegF 690 Acircmicromm-AcircdegC 383 Acircmicroinin-AcircdegF
Temperature 500 AcircdegC Temperature 932 AcircdegF
Specific Heat Capacity
0285 Jg-AcircdegC 00681 BTUlb-AcircdegF
Thermal Conductivity
167 Wm-K 116 BTU-inhr-ftAcircsup2-AcircdegF
Melting Point 1852 AcircdegC 3366 AcircdegF Boiling Point 4377 AcircdegC 7911 AcircdegF Optical Properties Metric English Comments
Emissivity (0-1) 032 032 650 nm unoxidized total
Processing Properties
Metric English Comments
Annealing Temperature
gt= 705 AcircdegC gt= 1300 AcircdegF cold-rolled in vacuum
gt= 760 AcircdegC gt= 1400 AcircdegF hot-rolled gt= 1000 AcircdegC gt= 1830 AcircdegF solution
annealing for forged billets
Component
Elements Properties
Metric English Comments
Zirconium Zr 100 100 Descriptive Properties
Alpha Phase hcp lt 870AcircdegC
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Crystal StructureBeta Phase Crystal Structure
bcc gt 870AcircdegC
CAS Number 7440-67-7
CHAPTER-3DESIGN
OVERVIEW
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
31 CMM DATA
311 GENERATION OF PRESSURE DISTRIBUTION DATA ON
THE BLADE
SURFACE
Last stage blade of steam turbine which is being analyzed for stress and vibration
is a highly twisted blade due to the variation if the blade speeds across the height of the
blade The deflection in the blade passage also reduces from hub to tip to vary the loading
on each section Thus the pressure distribution on the suction amp pressure surface of the
blade changes considerably from hub to tip to match the loading at that sectionIt is
known fact that the area of pressure distribution curve representing the blade loading
Hence it has been decided to generate the pressure distribution at all the lsquo17rsquo blade
sections
The following procedure allows to get the blade surface pressure distribution with the
help of BladeGen amp BladeGen plus package
From the blade coordinate input data file for suctionpressure surface x y z coordinate
of surface was generated as a loop with the following notations
X-along the height of the blade
Y- Meridional direction
Z-along blade to blade
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
2 Profile curve is generated with above coordinates of all sections placed one below
the other is sequence from section (1) to section (5 along the height of the blade The
coordinates between two section separated by lsquorsquo
3 Hub amp Shroud boundary is generated at the appropriate heights with ndashY negative
meridional axis corresponded from LE (Leading edge) And positive distance from
meridional distance from TE (Tailing Edge)
4 Hub Curve file is generated as follows
X Y Z
283450000 0000000000 -100000000
283450000 0000000000 0000000000
283450000 0000000000 1000000000
In between the values Comma is compulsory (X Y Z)
A profile contains total 60 points for all lsquo5rsquo sections
5 Profile Curve file is generated as follows
X Y Z
28345-574-2292
28345-523-2325
28345-446-2336
28345-343-2322
28345-215-2282
28345-066-2212
28345 103-2111
28345 285-1972
28345 474-1791
28345 661-1562
28345 832-1278
28345 966-939
28345 104-553
28345 1035-143
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
44265 1521-1551
44265 1564-1521
44265 1581-1469
44265 1574-1395
44265 1544-1299
44265 1491-1183
44265 1419-1049
44265 1326-899
44265 1214-736
44265 1079-566
44265 923-395
6 Shroud Curve File is generated as follows
44265 0 -100
44265 0 0
44265 0 100
32 LAYER OVER VIEW
A layer (or streamline) is defined as a meridional curve visible in the Meridional View
that represents surface of revolution Most layer types shown below represent curves
that are automatically created and updated as the Meridional Envelope (hub and shroud
curves leading and trailing edge curves) are modified
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig31 Single Blade
Layers serve two key purposes
1) Layers are referenced by the working views (Angle Thickness and PrsSct Views) to
provide the meridional location of the views data sets
2) Layers specify where streamline data sets are to be constructed for export
MERIDIONAL PROFILES
The meridional profile is primarily determined by a set of curve (Hub Shroud
inlet and outlet) This data is modified with leading and trailing edge curves (and other
meridional control curves) to describe an interpolation surface or grid in axial (z) and
radial co-ordinates vs stream wise (u) and span wise (v) positions This interpolation grid
is used when defining the layer that the meridional profile stores which are reference by
the angle thickness and prssct curves and used to define location of op data sets
ANGLE AND THICKNESS SPANWISE DISTRIBUTIONS
BladeGen offers several options for controlling the span wise distribution of angle and
thickness values These options can be displayed by clicking the right mouse button in
the Angle or Thickness View and selecting Span wise Distribution Type sub-menu from
the resulting popup menu Note that it is allowable for the Angle View to have a
different Span wise Distribution type than the Thickness View The following Span wise
Distribution types are available
General
Ruled Element
Axial Element
General
The General Distribution is the default Span wise Distribution type The
parameter of interest (angle or thickness) is defined by curves on defining layers that use
various meridional coordinates from those layers Since these layers may have arbitrary
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
shapes that dont necessarily correspond to true streamlines BladeGen must first convert
their coordinates to true meridional coordinates (consistent with the meridional
interpolation grid) before using them to compute the parameters to generate a blade
Ruled Element
The Ruled Element Span wise Distribution type is only available in the Angle
ViewIn a ruled element blade the angular location is defined by a straight line drawn in
3D space between points at the span location on the hub and shroud The hub and shroud
curves are the master curves They control the generation of all other defining curves
Thus the hub and shroud curves are the only curves that the user can modify in the Span
wise Distribution type
When one of the defining curves is updated from the hub curve it obtains its location by
the intersection of the surface of revolution generated using the meridional streamline and
the lines drawn between corresponding pairs of points on the hub and shroud Once this
update occurs a conversion is made to trueMeridional coordinates using the same
method as in the general Span wise Distribution type
Axial Element
In an axial element blade the parameter of interest (angle or thickness) depends
exclusively on radial position (R) at each span location The hub curve is the master
curve it controls the curves for all of the other defining layers Thus the hub curve is the
only curve that the user can modify in this Span wise Distribution type When a defining
layer curve is updated from the hub curve it obtains its parameter (angle or thickness) at
a given meridional position by using an axial projection from the hub curve Once this
update occurs a conversion is made to true meridional coordinates using the same
method as in the general Span wise Distribution type
When using axial element blades it is important to specify enough defining layers to
adequately describe the geometry of interest In most cases 5 layers are sufficientWhen
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
this distribution type is used in the Thickness View there is a menu command in the
popup menu to specify a taper angle The taper angle which normally defaults to zero is
limited to guarantee a minimum thickness of 10 of the specified value
Blade Settings
This section describes parameters and functions that apply to a single blade They are
accessed using either the Blade menu or the blade toolbar
BladeGen has the ability to design with splitter blades Splitter blades are blades
positioned between main blades for additional flow control Splitter blades can be
dependent on the main blade for their angular and thickness definitions or have their own
independent definitions
Like layers BladeGen has one active blade at a time Most views display only the data
pertaining to the active blade Only the Blade-to-Blade and 3D Views display all blades
AUXILIARY VIEW DETAILS
The Auxiliary View is used to display various data sets describing the model and is
automatically updated when modifications are performed in a Working View The values
displayed are calculated from the same data structures and functions that are used to
output geometry for other purposes
The following view types are available
Blade-to-Blade View
3D View
Meridional Contour View
Blade-To-Blade View
The Blade-to-Blade view shown below combines the meridional angular and
thickness descriptions of the blade along a streamline (called a layer) The blade is
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
displayed as a function of the distance along the streamline in the meridional view and its
angular position using one of three Coordinate Systems
Fig32 Blade-To-Blade ViewBlade-To-Blade View
3d View
This view allows the user to visualize the model in three dimensions as shown below
The model can be dynamically rotated panned and zoomed to achieve the desired
viewing perspective With material (surface) visibility and clipping plane controls the
user can choose to view a subset of the model in greater detail The user may also choose
to view multiple blades by using the replicates controls Like any other auxiliary view
the 3D view is automatically updated when a change is made in one of the working
views
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig33 3d-View Of A Twisted Blade3d-View Of A Twisted Blade
Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine Fig34 Total 3d-View Of An Axial Turbine RotorFront View Of An Axial Turbine
Fig35 Unstructured Mesh Model Of Rotor
Meridional Contour View
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
BladeGen allows the user to plot contours of Theta Beta Lean or Thickness on
the meridional profile as shown below This view can be displayed using the View |
Auxiliary View Content | Meridional Contour View menu command or by pressing the
toolbar button (located by default on the right edge of the main window)
The Contour view can display the following values Theta (Blade Location) Beta (Blade
Angle) Blade Lean Angle Normal Thickness and Modified Thickness (Includes
OverUnder-Filing)
The user can select from several grid densities Very Fine Fine Medium and Course
These settings use predetermined point counts which are distributed using the lengths of
the four edges of the blade
33 INTRODUCTION TO CAD
Computer-aided design (CAD) also known as computer-aided design and drafting
(CADD) is the use of computer technology for the process of design and design-
documentation Computer Aided Drafting describes the process of drafting with a
computer CADD software or environments provide the user with input-tools for the
purpose of streamlining design processes drafting documentation and manufacturing
processes CADD output is often in the form of electronic files for print or machining
operations The development of CADD-based software is in direct correlation with the
processes it seeks to economize industry-based software (construction manufacturing
etc) typically uses vector-based (linear) environments whereas graphic-based software
utilizes raster-based (pixilated) environments
CADD environments often involve more than just shapes As in the manual drafting of
technical and engineering drawings the output of CAD must convey information such as
materials processes dimensions and tolerances according to application-specific
conventions
CAD may be used to design curves and figures in two-dimensional (2D) space or curves
surfaces and solids in three-dimensional (3D) objects
CAD is an important industrial art extensively used in many applications including
automotive shipbuilding and aerospace industries industrial and architectural design
prosthetics and many more CAD is also widely used to produce computer animation for
special effects in movies advertising and technical manuals The modern ubiquity and
power of computers means that even perfume bottles and shampoo dispensers are
designed using techniques unheard of by engineers of the 1960s Because of its enormous
economic importance CAD has been a major driving force for research in computational
geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
systems to 3D solid and surfacemodelers Modern CAD packages can also frequently
allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
industrial structures (hospitals and factories)
CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
physical components but it is also used throughout the engineering process from
conceptual design and layout of products through strength and dynamic analysis of
assemblies to definition of manufacturing methods of components It can also be used to
design objects
CAD has become an especially important technology within the scope of computer-aided
technologies with benefits such as lower product development costs and a greatly
shortened design cycle CAD enables designers to lay out and develop work on screen
print it out and save it for future editing saving time on their drawings
Types of CAD Software
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CAD is an important industrial art extensively used in many applications including
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geometry computer graphics (both hardware and software) and discrete differential
geometry
Current computer-aided design software packages range from 2D vector-based drafting
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allow rotations in three dimensions allowing viewing of a designed object from any
desired angle even from the inside looking out Some CAD software is capable of
dynamic mathematic modeling in which case it may be marketed as CADD mdash
computer-aided design and drafting
CAD is used in the design of tools and machinery and in the drafting and design of all
types of buildings from small residential types (houses) to the largest commercial and
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CAD is mainly used for detailed engineering of 3D models andor 2D drawings of
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CAD has become an especially important technology within the scope of computer-aided
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Types of CAD Software
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Two-dimensional or 2D CAD is used to create flat drawings of products and structures
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Three-dimensional (3D) CAD programs come in a wide variety of types intended for
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Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
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desired designs
34 INTRODUCTION TO PROENGINEER
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DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
2D CAD
Two-dimensional or 2D CAD is used to create flat drawings of products and structures
Objects created in 2D CAD are made up of lines circles ovals slots and curves 2D
CAD programs usually include a library of geometric images the ability to create Bezier
curves splines and polylines the ability to define hatching patterns and the ability to
provide a bill of materials generation Among the most popular 2D CAD programs are
AutoCAD CADkey CADDS 5 and Medusa
3D CAD
Three-dimensional (3D) CAD programs come in a wide variety of types intended for
different applications and levels of detail Overall 3D CAD programs create a realistic
model of what the design object will look like allowing designers to solve potential
problems earlier and with lower production costs Some 3D CAD programs include
Autodesk Inventor CoCreate Solid Designer ProEngineer SolidEdge SolidWorks
Unigraphics NX and VX CAD PROENGINEER V5
3D Wireframe and Surface Modeling
CAD programs that feature 3D wireframe and surface modeling create a skeleton-like
inner structure of the object being modeled A surface is added on later These types of
CAD models are difficult to translate into other software and are therefore rarely used
anymore
Solid Modeling
Solid modeling in general is useful because the program is often able to calculate the
dimensions of the object it is creating Many sub-types of this exist Constructive Solid
Geometry (CSG) CAD uses the same basic logic as 2D CAD that is it uses prepared
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
solid geometric objects to create an object However these types of CAD software often
cannot be adjusted once they are created Boundary Representation (Brep) solid modeling
takes CSG images and links them together Hybrid systems mix CSG and Brep to achieve
desired designs
34 INTRODUCTION TO PROENGINEER
ProENGINEER Wildfire is the standard in 3D product design featuring industry-leading
productivity tools that promote best practices in design while ensuring compliance with
your industry and company standards Integrated ProENGINEER CADCAMCAE
solutions allow you to design faster than ever while maximizing innovation and quality
to ultimately create exceptional products
Customer requirements may change and time pressures may continue to mount but your
product design needs remain the same - regardless of your projects scope you need the
powerful easy-to-use affordable solution that ProENGINEER provides
ProENGINEER Wildfire Benefits
bullUnsurpassed geometry creation capabilities allow superior product differentiation and
manufacturability
bullFully integrated applications allow you to develop everything from concept to
manufacturing within one application
bullAutomatic propagation of design changes to all downstream deliverables allows you to
design with confidence
bullComplete virtual simulation capabilities enable you to improve product performance and
exceed product quality goals
bullAutomated generation of associative tooling design assembly instructions and machine
code allow for maximum production efficiency
Pro ENGINEER can be packaged in different versions to suit your needs from
ProENGINEER Foundation XE to Advanced XE Package and Enterprise XE Package
ProENGINEER Foundation XE Package brings together a broad base of functionality
From robust part modeling to advanced surfacing powerful assembly modeling and
simulation your needs will be met with this scalable solution Flex3C and Flex
Advantage Build on this base offering extended functionality of your choosing
DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
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DIFFERENT MODULES IN PROENGINEER
PART DESIGN
ASSEMBLY
DRAWING
SKETCHER
35 DESIGN OVERVIEW
351 DESIGN CONSIDERATIONS
Design will be created by considering the main consideration ie failures of the turbine
blade The break down and failures of turbo machineries have been influencing such as
consequential damages hazards to public life and most importantly the cost to repairs To
avoid these it is obvious that the balding of turbo machinery must be made structurally
stronger that means not in dimensions andor use of materials of construction but
keeping the operating stresses well within the limits
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Turbo machinery blades are classified into two categories depending on their
manner of operation as either impulse or reaction blades Impulse blades function by
redirecting the passing fluid (steam or gas) flow through a specified angle A work
producing force is developed by resulting change of momentum of passing fluid flow
Reaction blades function as airfoils by developing a gas dynamic lift from the
pressure difference which the airfoil causes between the blades upper and lower
surfaces High-pressure stages are generally impulse stages and low-pressure stages are
reaction stages Thus a single free standing blade can be considered as pre-twisted
continuous beam with an asymmetric airfoil cross-section mounted at a stagger angle on
a rotating disc
Failure of bladed disc
Excessive stresses
Resonance due to vibration
Operating environmental effects
Ever increasing demands of high performance together with reliability of
operation long life and lightweight necessitate consistent development of almost every
part of steam turbine blades from a vital part of a turbo machine Apart from their shape
and geometry on which the performance characteristics of the machine largely depend
their dynamic strength is of considerable importance as far as the reliability operation and
life of the engine are concerned High cycle fatigue plays a significant role in many
turbine blade failures During operation periodic fluctuations in the steam force occur at
frequencies
Corresponding to the operating speed and harmonics and cause the bladed disk to vibrate
The amplitude of these vibrations depends in part of the natural frequencies of the bladed
disk to the forcing frequency Large amplitude vibration can occur when the forcing
frequency approaches or becomes resonant with the natural frequency of the blades
Dynamic stresses associated with near resonant or resonant vibration produce high cycle
fatigue damage and can initiate and propagate cracks very quickly Steam turbine
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
manufacturers typically design and manufacture blades with adequate margins between
the forcing frequencies and the fundamental natural frequencies to avoid resonance
REASONS FOR FAILURES IN STEAM TURBINE BLADES
In the following paragraphs various failure modes of the turbine blade are discussed
along with different kinds of stresses in the blade and the nature of aerodynamic
excitation A brief discussion of each of the above failure mechanisms follows in order
to understand their significance
Excessive stress
The total stress at any location of the blade is sum of the centrifugal tension
centrifugal bending steady steam bending and the alternating bending The amplitude of
alternating bending depends on the dynamic bending force damping factor and the
resonant frequency Each of these is briefly discussed below to highlight their
importance
Centrifugal stress
In steam turbine centrifugal stress is never the main cause of a blade failure
except in the rare cases of turbine run-away or due to low cycle fatigue caused by
frequent start upsshut downs However centrifugal stress is an important contributing
factor with fatigue failure corrosion fatigue failure and stress corrosion failures The
level of centrifugal stress is kept at such a level so as to have enough margins for
alternating stress The blade configuration is designed so as to keep the center of gravity
of shroud airfoil and root attachments on a common radial axis This prevents
centrifugal induced torsion stresses Using any of the standard FEM packages can best
carry out analysis of centrifugal stress
Steam induced stress ndash steady state
Steam being the driving force exerts loads on the blade due to steam pressure
from the pressure side of the blade profile thereby inducing bending stresses This
bending stress is superimposed on the centrifugal tension Although the net value of
steady bending load and centrifugal stress alone is not normally a cause of blade failure
this is the basis for the majority of failures arising due to vibratory stresses superimposed
upon them
Steam induced stress ndash Alternating
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Steam induced alternating stress can be induced by interrupted arc of admission
nozzle wake at nozzle passing frequency mismatch of diaphragm nozzle at horizontal
split andor missing diaphragm blades nozzle pitch variation poor nozzle profile etc
Estimation of the vibratory stress caused by these requires the analysis of the response
of the blade to the excitation forces caused by these Obviously the inputs to such an
analysis are the excitation levels the damping natural frequency and the mode shape of
the blade vibration Disk vibrations which can get excited due to variety of reasons can
also cause high stresses in the blade roots leading to failure This aspect of blade
stressing is quite involved and many a time difficult to compute correctly
Impact stress
Impact stress arises due to entrapment of a foreign body such as broken valve
spindles strainers etc This may result in a chain reaction and can cause failure in many
downstream rotating and stationary blades Impact stress also results due to water ingress
and at times due to steam hammer and from rubbing of blades in the event of failure of
the thrust bearing
Low cycle fatigue
Low cycle fatigue is caused by frequent startstop operations thermal cycling and
frequent water slugging or water washing due to inadequate water drainage in the casing
and can cause failures within few hundreds to a few thousands stress cycle
Thermal fatigue
Thermal fatigues is a low cycle fatigue process as a result of thermal stress caused
due to quick starting rapid and frequent load changing steam temperature cycling and
water slugging Considerable thermal stresses are generated due to the temperature
differential since blade foil is in direct contact with the nozzle upstream temperature
whereas much cooler spent steam cools shroud root and disk
Creep stress
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Creep stress failures are rare but cracking at locations with high stress
concentrations may take place if design is inadequate Hence high temperature stages
should have larger fillet radii at the root
Resonant vibration
Vibration is important in designing turbine bladesdisk since resonant vibratory
stresses sustained over a period of time can cause fatigue failures The period of time
need not be large since a 500Hz vibration accumulates 2 million cycles in an hour and
108 cycles in 2 days Bladed disk poses a worst vibratory fatigue problem since it is
directly exposed to a wide range of aerodynamic excitation and failure can result when
any of the following matching takes place
A rotating turbine blade (bucket) is the components which converts the energy of
flowing fluid into mechanical energy Thus the reliability of these blades is very
important for successful operation of turbine Metallurgical examinations of failed blades
show that almost all the failures can be attributed to the fatigue of metal Fluctuating
forces in combination with the steady forces cause fatigue failure
Turbo machine experience fluctuating forces when they pass through non-uniform
fluid from stationary vanes (nozzle) The basic design consideration is to avoid or to
minimize the dynamic stresses due to fluctuating force Based on the vibration of the
mechanical structures the dynamic behavior of turbine blade blades or the bladed disc
assembly can be predicted
The present work presents an approach for modeling of blades bladed disc amp for
its vibration analysis Generally turbo machine low-pressure stage blades are long
twisted amp tapered so it needs lot of input data to accurately define the complete
geometry Blade geometry is defined by giving different profile data at
Different heights To reduce the pains for creation of solid model of this type of blades a
program file called as macro was developed in ansys command From these macros solid
model was created
Finite element method for the single blade solid model was created with eight
nodded quadrilateral brick element in ansys
Two types of analysis was done for this present work
Free standing blade static analysis
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Free standing blade model analysis
The maximum number of nodal diameters in bladed disc assembly is half the
number of blades (for an even number of blades) For the disc having an odd number of
the blades the maximum nodal diameter is (number of blades-1)2
For free standing blade root supports stiffness effect was studied and frequency at
different rotating speeds also calculated Analytical work to determine the blade
characteristics calls for accurately modeling the geometry
Results obtained through analytical work makes quite closely with experimental
work confirming the accuracy of the model and the adequacy of assumed boundary
conditions
352 DESIGN PROCEDURE
A turbo machine blade is usually a cantilever beam or plate is tapered and twisted with
an airfoil cross-section Typically a turbo machine has several stages each stage with a
stator and rotor In the stator they are all inserted as diaphragms or nozzles in a ring to
guide the flow medium at an appropriate entry angle into rotor blades The rotor blades
are mounted on a disc at a stagger angle to the machine axis and they convert the thermal
energy into mechanical energy in turbine In turbine steam enters at high pressure and
temperature in the first stage and expands while passing through the several stages before
it is let out from the last
Stage with low temperature and pressure after extracting as much as thermal energy as
possible Hence the short blades in high pressure have high frequency of the order of
1000Hz which becomes progressively lower about 100Hz in the last stage long blades
In the compressor stage the operation principle is reversed to compress the gases
utilizing the supplied mechanical power
A typical rotor blades sees upstream disturbances from the stator row and as it rotates
receives a corresponding number of increasing and decreasing lift and moment
alternating periodically depending on the number of stator bladesnozzlesguide vanes A
stator blade can also be imagined to rotate in an opposite direction to the rotor relative to
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
the moving row and thus receives a corresponding number of periodic forces and
moments equal to the rotor blades An ideal placement of blades in the stator is not
feasible in practice Firstly the blades are not all identical in their cross section along the
length their pitch distance from blade to blade varies and the axial and angular locations
will have some errors in mounting them in the stator housing Because of these errors in
the stator mechanical excitation at rotational speed and its harmonics occurs on the rotor
blades
Natural frequency and mode shape
Natural frequency is the frequency at which an object vibrates when excited by a force
such as a sharp blow from a hammer At this frequency the structure offers the least
resistance to a force and if left uncontrolled failure can occur Mode shape is the way in
which the object deflects at this frequency An example of natural frequency and mode
shape is given in the case of a guitar string When struck the string vibrates at a certain
frequency and attains deflection shape
The frequency can be noted by the pitch coming from the string Different string
geometries lead to different natural frequencies or notes By nature of its structure a
turbine blade has many natural frequencies and mode shapes These frequencies and
mode shapes are somewhat further complicated by the use of shroud to connect group of
blades together
MODEL PREPARATION AND FORMATION
Solid modeling is the first step for doing any analysis and testing and it gives physical
picture for new products FEM models can easily create from solid models by the
process of meshing FEM models can be made manually but it is for simple cases only
If the model is of complex shape only way for preparing FEM model is ldquomeshing the
solid modelrdquo
While dealing with complex blade structures such as blades with root or blades
with coupling from disc or shroud development of special purpose finite element
packages becomes too involved In those cases it becomes handy to adopt some well-
established finite element codes and couple them with information from aerodynamics
and damping models Some of the important commercial codes available are
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
NASTRAN ANSYS NISA SDRC I-DEAS etc here we will consider the application of
ANSYS software to model a Low Pressure last stage turbine blade with its root
Fig36 Assembly of CMM data by a curve
Fig37 CMM data free curves (3D CURVES)
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig38 solid blade view
Fig39 final model in 3D
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig310 final model in 2D
CHAPTER-4ANALYSIS
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
OFSTEAM TURBINE BLADE
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943 by R Courant who utilized
the Ritz method of numerical analysis and minimization of variational calculus to obtain
approximate solutions to vibration systems Shortly thereafter a paper published in 1956
by M J Turner R W Clough H C Martin and L J Topp established a broader
definition of numerical analysis The paper centered on the stiffness and deflection of
complex structures
By the early 70s FEA was limited to expensive mainframe computers generally owned
by the aeronautics automotive defense and nuclear industries Since the rapid decline in
the cost of computers and the phenomenal increase in computing power FEA has been
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
developed to an incredible precision Present day supercomputers are now able to
produce accurate results for all kinds of parameters
FEA consists of a computer model of a material or design that is stressed and analyzed
for specific results It is used in new product design and existing product refinement A
company is able to verify a proposed design will be able to perform to the clients
specifications prior to manufacturing or construction Modifying an existing product or
structure is utilized to qualify the product or structure for a new service conditionIn case
of structural failure FEA may be used to help determine the design modifications to meet
the new condition
There are generally two types of analysis that are used in industry 2-D modeling and 3-
D modeling While 2-D modeling conserves simplicity and allows the analysis to be run
on a relatively normal computer it tends to yield less accurate results 3-D modeling
however produces more accurate results while sacrificing the ability to run on all but the
fastest computers effectively Within each of these modeling schemes the programmer
can insert numerous algorithms (functions) which may make the system behave linearly
or non-linearly Linear systems are far less complex and generally do not take into
account plastic deformation Non-linear systems do account for plastic deformation and
many also are capable of testing a material all the way to fracture
FEA uses a complex system of points called nodes which make a grid called a mesh This
mesh is programmed to contain the material and structural properties which define how
the structure will react to certain loading conditions Nodes are assigned at a certain
density throughout the material depending on the anticipated stress levels of a particular
area Regions which will receive large amounts of stress usually have a higher node
density than those which experience little or no stress Points of interest may consist of
fracture point of previously tested material fillets corners complex detail and high
stress areas The mesh acts like a spider web in that from each node there extends a mesh
element to each of the adjacent nodes This web of vectors is what carries the material
properties to the object creating many elements
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
A wide range of objective functions (variables within the system) are available for
minimization or maximization
Mass volume temperature
Strain energy stress strain
Force displacement velocity acceleration
Synthetic (User defined)
There are multiple loading conditions which may be applied to a system Some examples
are shown
Point pressure thermal gravity and centrifugal static loads
Thermal loads from solution of heat transfer analysis
Enforced displacements
Heat flux and convection
Point pressure and gravity dynamic loads
Each FEA program may come with an element library or one is constructed over time
Some sample elements are
Rod elements
Beam elements
PlateShellComposite elements
Shear panel
Solid elements
Spring elements
Mass elements
Rigid elements
Viscous damping elements
Many FEA programs also are equipped with the capability to use multiple materials
within the structure such as
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Isotropic identical throughout
Orthotropic identical at 90 degrees
General anisotropic different throughout
Types of Engineering Analysis
Structuralanalysis consists of linear and non-linear models Linear models use simple
parameters and assume that the material is not plastically deformed Non-linear models
consist of stressing the material past its elastic capabilities The stresses in the material
then vary with the amount of deformation as in
Vibrationalanalysis is used to test a material against random vibrations shock and
impact Each of these incidences may act on the natural vibrational frequency of the
material which in turn may cause resonance and subsequent failure
Fatigueanalysis helps designers to predict the life of a material or structure by showing
the effects of cyclic loading on the specimen Such analysis can show the areas where
crack propagation is most likely to occur Failure due to fatigue may also show the
damage tolerance of the material
Heat Transfer analysis models the conductivity or thermal fluid dynamics of the
material or structure This may consist of a steady-state or transient transfer Steady-state
transfer refers to constant thermo properties in the material that yield linear heat
diffusion
41 INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis (FEA) software package Finite
Element Analysis is a numerical method of deconstructing a complex system into very
small pieces (of user-designated size) called elements The software implements
equations that govern the behaviour of these elements and solves them all creating a
comprehensive explanation of how the system acts as a whole These results then can be
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
presented in tabulated or graphical forms This type of analysis is typically used for the
design and optimization of a system far too complex to analyze by hand Systems that
may fit into this category are too complex due to their geometry scale or governing
equations
ANSYS is the standard FEA teaching tool within the Mechanical Engineering
Department at many colleges ANSYS is also used in Civil and Electrical Engineering as
well as the Physics and Chemistry departments
ANSYS provides a cost-effective way to explore the performance of products or
processes in a virtual environment This type of product development is termed virtual
prototyping
With virtual prototyping techniques users can iterate various scenarios to optimize the
product long before the manufacturing is started This enables a reduction in the level of
risk and in the cost of ineffective designs The multifaceted nature of ANSYS also
provides a means to ensure that users are able to see the effect of a design on the whole
behavior of the product be it electromagnetic thermal mechanical etc
42 ANALYSIS OF BLADES WITH DIFFERENT MATERIALS
Static analysis Chrome steel
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig41 The above image is imported from Pro-e to Ansys using IGES (Initial Graphical Exchange Specification) format
Fig42 The above image is showing meshing is used to divide the problem into
number of small problems and also to apply the material and element properties
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig43 The above image showing loads acting on spring
Fig44 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0147608 mm
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig45 The above image is showing vonmises stress value Vonmises stress
depends on vonmises theory of failure
Fig46 The above image is first mode shape of turbine blade having 11174
and also the first mode is considered as natural frequency of object
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig47 The above image is the second mode shape having frequency 2356
Fig48 The above image is the third mode shape having frequency 66537
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig49 The above image is the fourth mode shape having frequency 68111
Fig410 The above image is the fifth mode shape having frequency 12003
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Static analysisTitanium
Fig411The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0256561 mm
Fig412 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig413 The above image is first mode shape of turbine blade having
11154 and also the first mode is considered as natural frequency of object
Fig414 The above image is the second mode shape having frequency 23247
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig415 The above image is the third mode shape having frequency 64855
Fig416 The above image is the fourth mode shape having frequency 67216
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig417 The above image is the fifth mode shape having 118454
Thermal Analysis Chrome steel
Fig418 The above image is showing thermal loads
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig419 The above image showing the Temperature Distribution
Fig420 The above image is showing the Thermal Gradient sum
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig421The above image is showing the Thermal Flux sum
Thermal Analysis Titanium
Fig422 The above image is showing thermal loads
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig423 The above image showing the Temperature Distribution
Fig424 The above image is showing the Thermal Gradient sum
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig425 The above image is showing the Thermal Flux sum
Ceramic coating Static analysis
Fig426 The above image is imported from Pro-E to Ansys using IGES
(Initial Graphical Exchange Specification) format
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig427 The above image is showing distributed shape or variation of
geometry shape after applying loads The maximum displacement is 0430927 mm
Fig428 The above image is showing von-misses stress value Von-misses stress
depends on von-misses theory of failure
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig429 The above image is first mode shape of turbine blade having 10522 and
also the first mode is considered as natural frequency of object
Fig430 The above image is the second mode shape having frequency 2231
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig431 The above image is the third mode shape having frequency 60367
Fig432 The above image is the fourth mode shape having frequency 52926
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig433 The above image is the fifth mode shape having mode shape 116057
Thermal analysis of ceramic coating
Fig434 The above image is showing the thermal loads
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig435 The above image showing the Temperature Distribution
Fig436 The above image is showing the thermal flux
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Fig437 The above image is showing the thermal gradient sum
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CHAPTER-5RESULTS OF THE
ANALYSISON
BLADES
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
RESULTS TABLE
The results table is explained in the below graphs by comparing with each other
The values shown in the above table are taken from the thermal and structural analysis of
the blade using ansys software
The materials are shown in the graphs are listed as like mentioned below
1 Chrome Steel
2 Titanium
3 Cast Iron coated with Zirconium
chrome steel Titanium Cast Iron With Zirconium coating
Stress(Nmm2) 33907 327817 258892
Displacement(mm) 0147608 0256561 0430927
Temperature(degc) 533 533 533
Thermal gradient(degcmm)
715055 605119 72591
Thermal flux(Wmm2)
11727 10287 1597
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Stress(Nmm2)
1 2 30
50
100
150
200
250
300
35033907 327817
258892
Stress(N〖 mm〗 ^2)
Stress(N〖 mm〗 ^2)
The maximum stress applied on the blade is represented on the graph which will give a brief explanation that relatively it is low on the applied new material
Displacement(mm)
1 2 30
005
01
015
02
025
03
0147608
0256561
00430927000000001
Displacement(mm)
Displacement(mm)
The above chart explains that the displacement due to the stresses is less compared to generally used materials for the applied new material
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Temperature(degc)
1 2 30
100
200
300
400
500
600 533 533 533
Temperature(degc)
Temperature(degc)
Comparatively the temperature on the surface of the blade is same for all materials So this shows that there is nothing changed and no loss by introducing new material
Thermal gradient(degcmm)
1 2 30
100
200
300
400
500
600
700
8007150549999999
99
605119
72591
Thermal gradient(degcmm)
Thermal gradient(degcmm)
Relatively thermal gradient is less for the new applied material So it is an advantage for intro of zirconium coated cast iron
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
Thermal flux(Wmm2)
1 2 30
2
4
6
8
10
12
14
16
1172710287
1597
Thermal flux(W〖 mm〗 ^2)
Thermal flux(W〖 mm〗 ^2)
Relatively the thermal flux is high compared to other general materials So it is an advantage
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CHAPTER-6CONCLUSION
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CONCLUSION
In this project we have analyzed previous designs and generals of turbine blade to do
further optimization Finite element results for free standing blades give a complete
picture of structural characteristics which can utilized for the improvement in the design
and optimization of the operating conditions
In the first step we have designed turbine blade using CMM data from existing model
In the second step we have done the study on different materials which are suitable for
the improvement of turbine blade
In the third step we have validated our design using existing materials
In the next step we have applied different materials for turbine blade to suggest best
material
From the above results we can conclude that using cast iron with partially stabilized
zirconium coating is more beneficial than previous materials due to low stress
displacement good thermal strength low cost and easy to manufacture
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
CHAPTER-7BIBLIOGRAPHY
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
References
1 RaoJS application of variational principle to shrouded turbine blades
Proceedings of 19th cong ISTAM 1974 pp 93-97
2 LeissaAW MacbainJC and KeilbRE Vibration of twisted cantilever plates
summary of provisions current studies Journal of Sound and Vibration 1984
Vol-96 (20) pp 159-167
3 Tsuneo Tsuiji Teisuke Sueoka Vibrational analysis of twisted thin cylindrical
panels by using Raleigh-Ritz method JSME International Journal Series iii
1990 volume 33 pp 501-505
4 Le-Chung Shiau Teng-Yuan Wu Free vibration of buckled laminated plates
by finite element method Transactions of the ASME Journal of Vibrations
and Accoustics October 1997 volume 111 pp 635-644
5 Hu XX and TTsuiji free vibrational analysis of curved and twisted cylindrical
thin panels Journal of sound and vibration Jan7 1999vol-219 (1) pp 63-68
6 YooHH JYkwak and JChung Vibrational analysis of rotating pre twisted
blades with a concentrated mass Journal of sound and vibration Mar 2001
Vol 240(5) pp 891-908
7 Park Jung-Yong Jung Yong-Keun Park Jong-Jin Kang Yong-Ho
Dynamic analysis method for prevention of failure in the 1st stage low
pressure turbine blade with 2 fingers root Proceedings of SPIE - The
International Society for Optical Engineering 2001 vol 4537 pp 209-212
8 AHShah GSRamsekhar and YMDesai Natural vibrations of laminated
composite beams by using fixed finite element modeling Journal of sound
and vibration 2002 Vol 257 pp 635-651
9 JSRao RBahree AMSharan The design of rotor blades taking into
account the combined effects of vibratory and thermal loads transactions of
the ASME Journal of Engineering gas Turbines and Power oct-1989 vol-
111 pp 610-618
10 Wjkeartonsteam turbine theory and practice1992 7th edition pp423-450
- 2D CAD
- 3D CAD
- 3D Wireframe and Surface Modeling
- Solid Modeling
-
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