design and analysis of horizntal axis wind turbine blade...
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DESIGN AND ANALYSIS OF HORIZNTAL AXIS WIND TURBINE BLADE WITH 50
METER RADIUS A Postgraduate Project Report submitted to Manipal University in partial
fulfilment of the requirement for the award of the degree of
MASTER OF TECHNOLOGY
In
Computer Aided Mechanical Design and Analysis
Submitted by
PRAJWAL RAO K
Under the guidance of Dr Raj C Thiagarajan Dr. Satish Shenoy BManaging Director & Associate Professor ATOA Scientific tech, MIT,Manipal Bangalore
DEPARTMENT OF MECHANICAL AND MANUFACTURING ENGINEERING
MANIPAL INSTITUTE OF TECHNOLOGY (A Constituent College of Manipal University) MANIPAL – 576104, KARNATAKA, INDIA
June 2011
DEPARTMENT OF MECHANICAL AND MANUFACTURING ENGINEERING
MANIPAL INSTITUTE OF TECHNOLOGY (A Constituent College of Manipal University)
MANIPAL – 576 104 (KARNATAKA), INDIA
Manipal
CERTIFICATE
This is to certify that the project titled DESIGN AND ANALYSIS OF
HORIZNTAL AXIS WIND TURBINE BLADE WITH 50 METER RADIUS is a
record of the bonafide work done by PRAJWAL RAO K (Reg. No. 090922009)
submitted in partial fulfilment of the requirements for the award of the Degree of Master
of Technology (MTech) in COMPUTER AIDED MECHANICAL DESIGN AND
ANALYSIS of Manipal Institute of Technology Manipal, Karnataka, (A Constituent
College of Manipal University), during the academic year 2010-11.
Dr. Satish Shenoy B Project Guide
Prof. Dr. Divakara Shetty
HOD, Mech. & Mfg. M.I.T, MANIPAL
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ACKNOWLEDGMENTS
All the knowledge and experience which I gained during this period of project work would not have been possible without the wonderful support of some great personals. At this point I acknowledge and express my sincere gratitude to people who provided generous amount of support and guidance that helped me in completing this project successfully.
I am grateful and express my heartfelt gratitude to my guide Dr. Satish Shenoy, Associate Professor, Mechanical and Manufacturing Department, MIT, Manipal, for his patience, valuable advice, insightful comments, constant support and generous assistance during the course of this work. I express my sincere thanks to for his valuable suggestions and help rendered to me during the course of this project.
I heartily thank Dr Raj C Thiagarajan, Managing Director, ATOA Scientific Technologies Pvt Ltd, Bangalore for his thought provoking discussion and motivating suggestions which helped me to complete this project successfully.
I express my sincere thanks to S.J.Krishna Murthy Sc.'G' (Retd), Consultant, National Aerospace Laboratories, Bangalore, for helping me understand GH bladed software and for other valuable inputs.
I express my sincere thanks to S M Abdul Khader, Asst. Professor, Mechanical and Manufacturing Department, MIT, Manipal, for helping me understand Fluid structure interaction concepts and for other valuable inputs
I express my sincere thanks to Garrad Hassan & Partners Ltd, Bristol, BS2 0QD, UK, for providing the GH bladed Education version software for my analysis.
I would like to thank Dr. Kumkum Garg, Director, MIT and Dr. Divakara Shetty, HOD, Department of Mechanical & Manufacturing Engineering, MIT, for permitting me to avail all the resources and facilities available in the institute in completion of this project work. I also take the opportunity to thank our former HOD, Dr. N Y Sharma, Professor, for all the help provided during my postgraduate studies
I sincerely thank all the faculties of Manipal Institute of Technology for providing me with the foundation of the subjects which I had to fiddle with during the course of this thesis.
I thank all my classmates and friends for providing me with the support throughout the period of this study. Last but not the least I thank my parents and friends for their constant support and encouragement through the duration of this project work.
Prajwal Rao k
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ABSTRACT Wind turbines have now become one of the fastest growing forms of new electricity generation worldwide. In order to meet evolving mission needs in the area of wind power, it comes as no surprise that much of today's wind power research focuses on improving blade design of wind turbine, since this forms the critical part to yield more energy. Wind turbine blades, presently designed for 40 to 30m length or less. Since a turbine with long blades can capture more of the energy in the wind and therefore generate more electricity than a turbine with shorter blades, our study will consider a composite blade of 50m length.
Methodology used is Blade Element Moment theory which is theoretical method to calculate performance of wind turbine, Fluid structure interaction for coupled field analysis; CFD is used to determine aerodynamic loads and turbulence models are also used. Tools used are ANSYS classic, ANSYS CFX, FLUENT, and GAMBIT, GH Bladed.
Here we strive to determine the Total power developed and the aerodynamic load acting on blades during stall and rotating condition and thereby determining the stress and deflection of blade.
Three Mega watt of power can be produced with the new design. Present work gives the idea of loads acting on the blades and can be used for further improvement of design.
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LIST OF TABLES
Table No Table Title Page No 3.1 specification of ATO-MITB Wind turbine 8
3.2 Design codes with their aerodynamic features 12 3.3 Geometry of blade from root to tip 15 3.4 Material Property of Blade 17 3.5 Thrust force acting on blade at different incident velocity 25
4.1 Displacement for different Velocities 32 4.2 Deflection and von mises stress at different velocities 34 4.3 Comparison between coupled field analysis and Decoupled
analysis 36
4.4 Stress and deflection at different velocity of wind. 38 4.5 Stress and deflection at 12 m/s of wind 39 4.6 Comparison between Decoupled analysis FLUENT and
Theoretical 39
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LIST OF FIGURES Figure No Figure Title Page No
1.1 Vertical Axis wind turbine 1 1.2 Horizontal Axis wind turbine 2 1.3 Main component of HAWT 3 2.1 Size of wind turbine over the years 5 3.1 Work flow chart 9 3.2 Force diagram of flow over blade 9 3.3 Input file for WT_Perf code 13 3.4 Code run in DOS PROMPT 13 3.5 Output file from WT_Perf code 13 3.6 GH bladed settings 14 3.7 Isometric view of blade created in ANSYS 15 3.8 Blade at different station from root 16 3.9 2D Model of airfoil and fluid around it 18 3.10 FLUENT analyses for 2.22 degree twist 18 3.11 Validation of result using xfoil code 19 3.12 Pressure coefficients over the airfoil 19 3.13 Sorting in excel and applying it on nodes of blade in ANSYS 20 3.14 Final applied forces on all nodes of blade in ANSYS 20 3.15 Blade after applying boundary condition 21 3.16 Force distribution on blade planform 21 3.17 Model of Blade in GAMBIT 22 3.18 Model of Fluid in GAMBIT 23 3.19 Model of Fluid and Blade in ANSYS-CFX 23 3.20 Aerodynamic load from FLUENT acting on blade in ANSYS 24 3.21 Thrust force applied on blade 25 4.1 TSR Vs Coefficient of Power (Theoretical) 26 4.2 Velocity Vs Power (Theoretical) 26 4.3 TSR Vs Coefficient of Power (WT_Perf code) 27 4.4 Velocity Vs Power (WT_Perf code) 27 4.5 TSR Vs Coefficient of Power (GH Bladed) 28 4.6 Velocity Vs Power (GH Bladed) 28 4.7 TSR Vs Coefficient of Power (Comparison) 29 4.8 Velocity Vs Power (Comparison) 29 4.9 TSR Vs Thrust Force (Comparison) 30 4.10 TSR Vs Thrust Coefficient (Comparison) 30
4.11 Displacement at 50 m/s 31
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4.12 Displacement at 36 m/s 31 4.13 Displacement at 60 m/s 32 4.14 Displacement at 60 m/s 33 4.15 Von mises stress at 60 m/s 33 4.16 Displacement at 50 m/s 33
4.17 Von mises stress at 50 m/s 33
4.18 Displacement at 36 m/s 34 4.19 Von mises stress at 36 m/s 34
4.20 Plot of displacement at 36 m/s 35 4.21 Plot of Von mises at 36 m/s 35 4.22 Plot of displacement at 50 m/s 35 4.23 Plot of Von mises at 50 m/s 35 4.24 Plot of displacement at 60 m/s 36 4.25 Plot of Von mises at 60 m/s 36 4.26 Displacement at 12 m/s 37 4.27 von mises at 12 m/s 37 4.28 Displacement at 10 m/s 37 4.29 von mises at 10 m/s 37 4.30 Displacement at 8 m/s 38 4.31 von mises at 8 m/s 38 4.32 Displacement at 12 m/s 39 4.33 von mises at 12 m/s 39
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Contents Page No
Acknowledgement iii Abstract iv List Of Tables v List Of Figures vi
Chapter 1 INTRODUCTION 1.1 INTRODUCTION 1 1.2 MOTIVATION 1 1.3 TYPES OF WIND TURBINE 1 1.4 COMPONENTS OF WIND TURBINE 3 1.5 DEFINATION OF THE PROBLEM 4 1.6 OBJECTIVE OF THE STUDY 4 1.7 SCOPE OF STUDY 4
Chapter 2 BACKGROUND THEORY 2.1 LITERATURE REVIEW 5 2.2 SUMMARY OF LITERATURE REVIEW 7
Chapter 3 METHODOLOGY 3.1 ATOA-MIT WIND TURBINE BLADE (ATOA-MITB) 8 3.2 SPECIFICATION OF ATOA-MITB WIND TURBINE 8 3.3 AERODYNAMIC ANALYSIS 8 3.4 STRESS ANALYSIS OF ATOA-MITB 15
Chapter 4 RESULT ANALYSIS 4.1 AERODYNAMIC ANALYSIS 26 4.2 DECOUPLED ANALYSIS AT PARKED CONDITION (FLUENT) 31 4.3 DECOUPLED ANALYSIS AT PARKED CONDITION (THEORETICAL) 33 4.4 RESULTS OF FSI 35 4.5 DECOUPLED ANALYSIS AT OPERATING CONDITION (FLUENT) 37
4.6 DECOUPLED ANALYSIS AT OPERATING CONDITION (THEORETICAL)
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Chapter 5 CONCLUSION AND FUTURE SCOPE 5.1 WORK CONCLUSION 40 5.2 SCOPE OF FUTURE WORK 40
REFERENCES 41 PROJECT DETAILS 42
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LIST OF SYMBOLS Symbol Abbreviation
a Axial induction factor
a` Angular induction factor
B Number of blades
c Aerofoil chord length (m)
CL Lift coefficient
CD Drag coefficient
CP Power coefficient
P Power (W)
r ,r radius and radial direction (m)
R Blade tip radius (m)
V Absolute velocity (m/s)
β Relative flow angle onto blades (Degree)
λ Tip speed ratio
λr Local Tip speed ratio
η Mechanical/electrical efficiency
ρ Density (kg/m3)
σ` Local Solidity
Ω Blade rotational speed (rpm)
γ Aerofoil inlet angle (Degree)
TSR Tip speed ratio
Ct Coefficient of Thrust
T Thrust Force (N)
CHAPTER 1 INTRODUCTION
1.1 Introduction
Rate at which the fossil fuel is been used or rate at which it’s depleting, sooner or later we have to focus our attention in large scale towards renewable energy resources like wind or solar. Over the decades scientific technology for extracting renewable energy resources like wind energy has improved dramatically. Wind energy is the fastest growing renewable energy and in many ways, attempts have been made to extract this energy from wind. One such method is by using wind turbines. Wind turbines play a major role in extracting energy from wind in the form of electricity.
1.2Motivation In order to achieve lower cost per kW using wind turbine the size of wind turbine nowadays has increased dramatically. With modern computing facility and available memory complex model can be generated and analyzed easily. In this project, we have done design and analysis of wind turbine blade with 50m radius.
1.3 Types of Wind turbine Wind turbines can be categorized into two overarching classes based on the orientation of the rotor.
1.3.1 Vertical Axis wind turbine 1.3.2 Horizontal Axis wind turbine
1.3.1 Vertical axis wind turbine (VAWT): As shown in Fig: 1.1, this is a type of wind turbine where the main rotor shaft is set vertically.
Fig: 1.1 Vertical Axis wind turbine
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Advantage and disadvantage of VAWT
Disadvantages
• Rotors generally near ground where wind poorer
• Centrifugal force stresses blades
• Poor self-starting capabilities
• Requires support at top of turbine rotor
• Requires entire rotor to be removed to replace
bearings
• Overall poor performance and reliability
• Have never been commercially successful
Advantages
• Omni-directional
• Accepts wind from any angle
• Components can be mounted at ground level
o Ease of service
o Lighter weight towers
• Can theoretically use less
1.3.2 Horizontal axis wind turbine (HAWT): As shown in Fig: 1.2, this is a type of wind turbine in which the axis of the rotor's rotation is parallel to the wind stream and the ground. HAWT are built with two or three blades, although some have fewer or more blades.
Fig: 1.2 Horizontal Axis wind turbine
HAWT has exhibited good performance and has been commercially very successful because of these reason we have selected HAWT in our project work.
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1.4 Components of wind turbine In general wind turbine consists of a number of components in it. The main components of a wind turbine are shown in Fig: 1.3 can be divided into three main categories, Rotor, Nacelle and Tower.
Fig: 1.3 Main component of HAWT
1.4.1 Rotor
The portion of the wind turbine that collects energy from the wind is called the rotor. The rotor usually consists of two or more wooden, fibreglass or metal blades which rotate about an axis (horizontal or vertical) at a rate determined by the wind speed and the shape of the blades. Also it consists of extenders that attach the blades to the central hub and Pitch drives to control the angle of the blades.
1.4.2 Nacelle
Nacelle is the housing on top of the tower, which contains Generator, Gear-box, High-speed and low-speed shaft, controls and brake assemblies inside it. Generator converts the turning motion of a wind turbines blade into electricity. Inside the generator coils of wire are rotated in a magnetic field to produce electricity. Generators typically require rpm’s of 1200 to 1800. As a result most wind turbines require a gear-box transmission to increase the rotation of the
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generator to the speeds necessary for efficient electricity production. Brakes are used to stop the rotation of the rotor at storm wind conditions and during maintenance.
1.4.3 Tower
The tower on which a wind turbine is mounted is not just a support structure. It also raises the wind turbine so that its blades safely clear the ground and so it can reach the stronger winds at higher elevations. Maximum tower height is optional in most cases, except where zoning restrictions apply. The decision of what height tower to use will be based on the cost of taller towers versus the value of the increase in energy production resulting from their use.
1.5 Definition of the Problem
To design and analyze a 50 meter wind turbine blade and to study its performance.
1.6 Objective of the Study
Our present study concentrates on designing a wind turbine blade of 50m radius and carry out aerodynamic analysis and also to predict the stress distribution over the blade during the operating conditions and during gust condition when the rotor blade is parked.
a. FSI and decoupled analysis are used for prediction of deflection and stress under parked condition
b. Decoupled analysis is used for prediction of stress under operating conditions.
1.7 Scope of the Study Turbine blades experience variable aerodynamic loads, potentially causing adverse effect on structures, mechanical components and power production. The study carried out on a 50m radius blade gives a good understanding of the loads experienced and can be evaluated for further developments of wind turbines. Aerodynamic analysis is done using BEM theory and stress distribution is done using conventional decoupled method and FSI for parked condition of blade and decoupled analysis is done for operating condition.
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CHAPTER 2 BACKGROUND THEORY
Wind turbine Industry is rapidly growing industry. Lower cost, environment friendly large wind turbines (Fig: 2.1) and with improved design, efficiency of wind turbine to generate power has gone significantly higher.
Fig: 2.1: Size of wind turbine over the years 2.1 LITERATURE REVIEW J.F.Manwell, J.G.McGowan and A.L.Rogers [1] is a book in which they have discussed the basic about rotor aerodynamics and rotor design. They have given mathematical models and derivations for development of power and relationship between flow over rotor and its blade, briefly introduces to the concept of Betz limit, also covers a broad area on the Structural dynamics of wind turbines including system engineering model, blade equations of motions, blade and hub loads, instabilities and load specification. S. Lain, B. Quintero and Y. Lopez [2] have discussed about 50m blade aerodynamic and its results. Structural dynamics analysis and aeromechanical evaluation of large horizontal axis wind turbine is done in this paper. The strategy is based on the combination of an aerodynamic model which provides the three-dimensional pressure distribution on the HAWT’s blades, and structural module which takes such pressure force as input data in order to compute blade deformation strain and stress over the blade. Geometry of rotor/blade for our design was taken from this publication.
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Grant Ingram [3 ]has given brief explanation on Momentum theory and Blade element theory and finally combined above two to give generalized strip theory(Blade element Momentum theory(BEM)).This theory which is Engineering method to calculate flow over rotor and blade and also to calculate power is used in our work.
Jan van der Tempel and David-Pieter Molenaar [4] to translate the basic model to a wind turbine system, first excitation frequencies are to be examined. The most visible and present source of excitation in a wind turbine system is the rotor. Here they have considered an example of constant speed wind turbine. The constant rotational speed is the first excitation frequency, mostly referred to as 1P. The second excitation frequency: NbP in which Nb is the number of rotor blades. This means 2P for a turbine equipped with two rotor blades and 3P for a three bladed rotor. Also a discussion is being carried out by the authors for varying loads acting on wind turbine blades.
Marshall L. Buhl, Jr., Alan D. Wright, James L. Tangler [5] have discussed about different design codes designed by National wind technology centre of the National Renewable Energy Laboratory for the analysis of wind turbine. In this paper they have compared the aerodynamic loads for three programs: Garrad Hassan’s Bladed, our own WT_Perf, and the University of Utah’s Yawdyn. Ryan T. Cowgill, Jake Fouts, Byron Haleyand Chris Whitham[6] have discussed about the use of WT_Perf code, creation of airfoil input files, resulting output files.
RamanandaPrabhu N [7]
, Analysis of CARTER 300kW wind turbine blade. In this thesis
steady state stress analysis and modal analysis. Aerodynamic analysis using Bladed software is done.
Lionel Anup Noronha [8], Extended analysis of CARTER 300kW wind turbine blade is done
and FEM analysis of NAL 500KW wind turbine is also carried out.
Ira H. Abbott and Albert E. Von Doennhoff [9] have discussed in about lift/drag of different
airfoil profiles determined experimentally. This is used to validate with the values obtained for lift and drag using FLUENT.
Nian-Zhao Jiang,Xiang-Lin ma,Zhi-qing Zhang[10]
have built 3D model of rotor blade using ANSYS. Static strength and dynamic character have been analyzed. Aerodynamic and centrifugal force both have been considered.
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Z.L.Mahri,M.S.Rouabh[11]
Blade element theory was used to calculate aerodynamic loads. Modal analysis of rotor was done using FEM and also by blade motion equation to compute mode shapes and frequency. Dynamic stress analysis for root region of blade was done using FEM. Chenvu zhang, Simon wang and Huimin xie [12]
Blade is created in GENSIS and static and Dynamic stress analysis for root region of blade was done using FEM. Mark Drela [13], has discussed about the generation of input file for WT_Perf code and reading of its output file.
G. Bir and P. Migliore [14] have discussed about preliminary structural design of composite wind turbine blades. Also discussion is carried out on the technical approach covering blade design and computation of its structural properties.
Rajesh Bhaskaran[15],has given in his web site the use of FLUENT for calculation of CL and CD for different inlet angles of wind. This method is used to calculate aerodynamic forces on wind turbine blade in our design. Germansheir Lloyd [16] has given the basic rules and guidelines for building a new wind turbine.
2.2 Summary of literature Review Much of past work done is on wind turbine blade with radius 40 to 30m or less and in many publications Blade element moment theory is widely used for aerodynamic analysis.
Conventional decoupled method is used for stress strain analysis and to calculate deflections of wind turbine blades. Fluid structure interaction which is a coupled field method is not used in many of the cases.
CHAPTER 3 METHODOLOGY
3.1 ATOA-MIT WIND TURBINE BLADE (ATOA-MITB) Wind turbine blades, Nowadays are designed for 40 to 30m radius or less. Since a turbine with long blades can capture more of the energy in the wind and therefore generate more electricity and cost per kw will be much lesser than a turbine with shorter blades. Our new design which is henceforth termed as ATOA- MIT Blade (ATOA-MITB) is of blade radius 50m.
3.2 SPECIFICATION OF ATOA-MITB WIND TURBINE
Table: 3.1 specification of ATO-MITB Wind turbine
Type of Turbine Horizontal Axis/ upwind Rated Power 3MW @ wind speed of 12m/s Rotational Speed 11 rpm (1.12 rad/Sec) Cut in speed 4.0 m/s Cut out wind speed 24.0 m/s
Rotor
Rotor diameter 100 m Number of blades 3 Blades
Type ATOA-MITB Material Graphite Epoxy Blade Design Non linear Twist Taper
Profile NACA 0012
3.3 AERODYNAMIC ANALYSIS
3.3.1 Theoretical Calculation
Aerodynamic analysis of ATOA-MITB Using BEM theory we have calculated coefficient of power (Cp), total Power (P), coefficient of thrust (Ct) and thrust force (T) is done for different
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incident velocity. Outcome of this results are validated with WT_Perf code and GH bladed software.
3.3.2 Work flow block diagram
Fig: 3.1Work flow chart
3.3. 3 Formulas
The above flow chart (Fig: 3.1) utilizes
following formulas
1) Blade tip speed ratio
•
2) Local speed ratio Fig: 3.2 Force diagram flow over blade
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3) Where σ` is called the local solidity and is defined as:
• `
4) Relative flow angle onto blades airfoil
90 tan •
1 `
• φ = 90-β
5) The angle of attack (i/α) is defined by the angle of relative wind (φ) and the section pitch
angle (ξ)
• i/α= φ – ξ
Or
• The angle of attack (i/α) =γ-β; (γ- Aerofoil inlet angle assumed)
6) Examining the NACA 0012 Lift and Drag Coefficient plot, gives a lift coefficient (CL). Or CL can also be obtained from CFD panel flow method (by running XFOIL code) or by using FLUENT software.
7) First guess for a and a` to calculate “first guesses” for these two parameters.
•
`•
8) Iteration 1
• Use a and a’ calculate beta
tan•
• φ= 90-β
• i/α= φ – ξ, Or
• Incident angle(i/α)= λ-β
• Examining the NACA 0012 Lift and Drag Coefficient plot, gives a lift coefficient
(CL). Or
• CL can also be obtained from CFD panel flow method (by running XFOIL code)by
using FLUENT software
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• Calculate new values of a and a`
• 1 `
` `
• 1
Iteration is repeated till difference between successive values of a and a’ diminishes as the
solution progresses, to acceptable values.
9) Calculate Coefficient of performance:
• ` 1
That Trapezium rule: • 2
` 1
The power coefficient for different incident velocity is calculated.
is obtained in each case.
Power for different incident velocity:
we calculate power at different velocity.
•
We set n = 1 and repeat for each portion of the blade. So x will be replaced by λr and f (x) =
for each element. The calculation of power coefficient is shown in work sheet.
Similar calculations are repeated for different incident velocities and Cp
10)
Once C value for each incident velocity is finalizedp
P = Cp η ( ) ρ (π)R V
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η- Mechanical efficiency taken 0.9 from literature [3]
11) Thrust coefficient (Ct)
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•
11) Thrust Force (T)
AV2 [4a(1-a)]
used for calculation results are presented chapter 4.1.1
• T= (1/2) ρ
These above formulas are
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To check ed with the once obtained with WT_Perf code and GH Bladed for the input data as given in
[2]
A variety of design alternatives are available for aerodynamic design of Wind turbine. The nology Centre (NWTC) of the National Renewable Energy Laboratory
Aerodynamic Feature BLADED WT_Perf YawDyn
the correctness of the present code or calculation the results obtained are compar
literature .Explanation of the same is presented in chapter 4.1.4 and 4.1.5.
3.3.4 WT_Perf code
National Wind Tech(NREL) is developed several computer codes used to design and analyze wind turbines.
Prominently used Design codes [5]
with their aerodynamic features are listed in Table: 3.2.
Table: 3.2 Design codes with their aerodynamic features
Induction, Axial Optional Optional Optional Induction, Tangential Optional Optional Optional Loss Factor, Hub Optional Optional Not available Loss Factor, Tip Optional Optional Always enabled Wind Shear Optional Optional Optional Tower Shadow Optional Not available Optional
We selected WT_perf code for our design, WT mance evaluation software for orizontal Axis Wind Turbines. It is written in FORTRAN 95 by Marshall L. Buhl, Jr. from
_Perf is perforHNational Renewable Energies Laboratory This software is designed to produce a performance prediction of a wind turbine rotor based on the geometric dimensions of the blade/rotor. This software is designed to be run in a DOS environment. The software uses a blade element momentum theory to iterate the performance characteristics on both a blade element level (section of constant airfoil) and on an overall turbine performance level. This software has been certified accurate by the National Renewable Energy Laboratories according to Buhl[5] . In order to use the program with the specific airfoils chosen, it was necessary to create Airfoil Input Files that related the lift, drag, and moment coefficient with variations in angle of attack of each of the airfoils. Since the data was published on the NREL website, the Airfoil Input files were created by interpolating values from the published charts. The files were then executed for
the desired geometry and site characteristics using WT_Perf[6].Results are presented in chapter
4.1.2.
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Fig: 3.3 Input file for WT_Perf code Fig: 3.4 Code run in DOS PROMPT
Fig: 3.5 Output file from WT_Perf code
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3.3. GH BLADED Software
Bladed provides worldwide wind turbine and component manufacturers, certification agencies, design consultants and research organizations with a design tool that has been extensively validated against measured data from a wide range of turbines. It enables users to conduct the full range of performance and loading calculations. With a Windows-based user interface, it supports calculations of combined wind and wave loading, with full aero elastic and hydro elastic modeling. It has been validated by Germanischer Lloyd for the calculation of wind turbines loads for design and certification. Values are fed to software and results are obtained.
Fig: 3.6 GH bladed settings
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3.4 STRESS ANALYSIS OF ATOA-MITB
3.4.1 Geometry of Blade
Geometry of blade from root to tip is given in table 3.3. It can be seen from table that NACA profile is been used from root till tip with non linear-taper and twist. Chord at root of blade is maximum and it reduces toward tip. Total of 9 stations considered in our analysis.
Fig: 3.7 Isometric view of blade created in ANSYS
Table: 3.3 Geometry of blade from root to tip
Radius [m]
Pitch [degrees]
Chord [m]
Profile
11.20 14.00 5.450 NACA001218.75 6.27 4.825 NACA001226.05 2.22 4.225 NACA001232.75 0.69 3.670 NACA001238.65 0.17 3.185 NACA001243.45 0.03 2.790 NACA001247.08 0.00 2.495 NACA0012
49.25 0.00 2.310 NACA0012
50.00 0.00 2.250 NACA0012
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Fig: 3.8 Blade at different station from root
3.4.2 Finite Element Modeling
Stress analysis has been carried out on the rotor blade. It’s a 3 bladed wind turbine but under uasi-static analysis loads are also symmetric like blade geometry. Therefore it is sufficient to
mation study. The finite element modeling carried out is described briefly in the following paragraphs.
lade fo namic surface. The blade is made up of orthotropic of Graphite Epoxy l. It h ge twist n root a m root to tip. FEM Model of the blade is (see .7).NACA 0012 airfoil is been used. Coordinate of airfoil is imported to
S. Cu re created thes translated and rotated. Area is created rves a lume of bla nerat
ypes o s and speci
ind-tu designer’s rucial blade design, since the principal loads originate from the rotor. That’s the reason so much effort is placed on the statics and dynamics of
ind t blade. It is to n loading regime of the wind turbine rotor properly specified; acc hing design will be more than a routine task.
After a preliminary design has been chosen, the blade structure is estimated and arbitrarily ecified so that the loads can be calculated for its assumed weight, stiffness, type of material
and dimensions. The loads in any of the members of a wind turbine fall into one of the following three categories,
a. Inertial forces b. Aerodynamic forces c. Structural Forces
qanalyze only one blade for the stress and defor
The b rms aerodymateria as a lar ear the nd tapers froshown Fig: 3ANSY rves a through e points thenfrom cu nd vo de is ge ed.
3.4.3 T f load fication
The w rbine most c task is the
the of w urbine enough ote that if thecan be omplis an adequate
sp
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3.4.4 Steady Loads on Wind Turbine Blades The wind Turbine operates over a wide range of loads but the analysis is performed for a few
n the wind turbine experience steady load due to its own self weight). The gust load on the blade can be assumed steady with some factor
sing FLUENT
the blade, to avoid damage we apply mechanical brakes
lade made of laminated Graphite Epoxy with NACA 0012 has following properties.
Table 3.4 Material Property of Blade
Graphite Epoxy
critical conditions. The blade experiences foremost critical load during the gust condition during which brake is applied and blade rotation is prevented. The other loading condition taken up is the operating situation. In windy conditions in the field the load acting on the wind turbine is never steady. (Only in the calm non-windy conditio
for dynamic loading. Similarly, during the operation of wind turbine uniform wind field is assumed ignoring the wind shear and turbulence and stress analysis is carried with elaborate finite element of the model.
3.4.5 Decoupled analysis at parked condition u
When high wind blows (Gust) across that’s when parked condition of blade arises. It is critical to analyze the forces acting on blade when blade is parked to avoid catastrophic failure. We calculated what maximum deflection blade can undergo during this condition and what would be the maximum stress developed.
The conventional way of finding displacement and stress on blade under parked condition is decoupled analysis. In which pressure or forces acting on blade at different station from root is determined independently and later these forces are applied on nodes of blades in ANSYS.
An Orthotropic b
Material Properties
E1 (G Pa) 145 E2 3 =E (G Pa) 10 ν12=ν23=ν13 0.25 G12=G23= G13(G Pa) 4.8 ρ (Kg/mm3 ) 1580e-9 Aerodynamic loads acting on blade at parked condition is determined using GAMBIT and FLUENT. This forces are extracted in excel sorted and aerodynamic forces are applied on the nodes of blade in ANSYS. Deflection of blade due to these forces is noted down. This method of determining the deflection is known as decoupled method.
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For 50 m/s velocity, for pitch 2.22, a 2D model was created in GAMBIT and meshed
Fig: 3.9 2D Model of airfoil and fluid around it
and solved to get CL and CD
Fig: 3.10 FLUENT analyses for 2.22 degree twist
The mesh was exported into FLUENT
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Fig: 3.11 Validation of result using xfoil code
The lower curve is the upper surface of the airfoil and has a negative pressure coefficient as the ressure is lower than the reference pressure. Exported values of forces on nodes through
FLUENT, sorted in excel then applied to the nodes of blade in ANSYS.
Fig: 3.12 Pressure coefficients over the airfoil
p
19
Fig: 3.13 Sorting of values in excel and applying it on nodes of blade in ANSYS
Similarly calculation for 6.27, 0.69, 0.17, 0.03, 0.00 stations are done for given velocity. All values of forces on different nodes are extracted from FLUENT, sorted in excel then applied to the nodes of blade in ANSYS
Fig: 3.14 Final applied forces on all nodes of blade in ANSYS
20
21
Settings in ANSYS Element type: Solid45 ADOF = 0, is applied at the root Forces from FLUENT is applied at different stations from root as shown in Fig: 3.15
Fig: 3.15 Blade after applying boundary condition Results are presented in chapter 4.2
the wind turbine is found using equation below, to simulate thrust due to gust.
Fgust = CD*½ (ρ*A*Vgust2)
Vgust = wind velocity at gust condition.
Dynamic pressure = *½ (ρ*Vgust2)
Drag Co-efficient = CD= 1.38
Blade Planform area = A= m3
Fig: 3.16 Force distributions on blade planform
3.4.6 Decoupled analysis at parked condition (Theoretical)
Initially the dynamic pressure for
Density of Air = ρ = 1.25kg/m3
This force acts unifoblade is divided into seentire surface according to the plin FEM analysis under gust loading. The Deflection and stress values obtained fo
rmly over the planform area of the blade. The whole planform area of the veral small areas, along the span and the force is distributed over the
anform area of each section.The same distribution is simulated r blade for
velocity 60m/s,50m/s and 36m/s is shown in figures below.Results are presented in chapter 4.3.
3.4.7 Fluid - Structure Interaction of Wind turbine under parked condition
Coupled field method, i.e., Fluid structure interaction for parked blade is also done in which model of blade and fluid element is done using GAMBIT and FSI is done with help of ANSYS CFX software. Deflection and stresses developed are noted down and verified with decoupled method.
To do analysis of wind turbine blade under parked condition we use Fluid structure interaction method. We carried out analysis of one blade considering it to be fixed at one end and fluid (air) passing around it at different velocities.
In Present day calculation for parked condition, pressure acting on blade is calculated separately and this pressure values are applied on nodes of blade in ANSYS. This is effective but doesn’t
ives more accurate values, hence in e Used ANSYS CFX as tool. An orthotropic
NACA 0012 profile and property as shown in able 3.3 with geometry as shown in Table: 3.2.
GAMBIT. Coordinates of NACA 0012 was imported, gh this points. These curves are translated and rotated. Areas are
volume is generated. Blade is the meshed with Quad element.
Fig: 3.17 Model of Blade in GAMBIT
give accurate values of deflection and stress. Whereas FSI gour analysis we have used FSI method and we havblade made of laminated Graphite Epoxy withT
3.4.7.1 Modeling of Blade and Fluid Element
Blade
Model of structure (Blade) was created incurves where created throucreated through this curves and
22
Fluid Fluid element (region of air around the blade) was created in GAMBIT and meshed as shown
Fig: 3.18 Model of Fluid in GAMBIT
These models are exported to ANSYS-CFX for FSI analysis.
Fig: 3.19 Model of Fluid andStress distribution and deflection of blade are presented in chapter 4.4
Blade in ANSYS-CFX
23
3.4.8 D
Decoupled analysis is done for blade in operating condition. Aerodynamic forces acting when in
ecoupled analysis at operating condition using FLUENT
operating conditions are determined with GAMBIT and FLUENT. Maximum power output for 50 meter radius blade under operating condition will be at velocity 12m/s as can be seen from aerodynamic analysis. Aerodynamic forces are calculated using GAMBIT and FLUENT for velocity of 12m/s. These values are exported to nodes of blade in ANSYS classic; these steps are similar to the aerodynamic analysis of parked blade using FLUENT. In addition to aerodynamic force we apply centrifugal force to the blade. Centrifugal force i.e., value of omega equal to 1.12 rad/s is given in ANSYS about the global. Displacement and von mises stress are noted down and are presented chapter 4.5.
Fig: 3.20 Aerodynamic loads from FLUENT acting on blade in ANSYS
3.4.9 Decoupled analysis at operating condition theoretical method
Maximum power output of 3MW is obtained at wind velocity of 12 m/s. At this velocity thrust force is calculated from BEM theory. This thrust force are applied on the nodes of the blade from root to tip and resultant stress and deflection of blade are found.
24
25
ity Table: 3.5 Thrust force acting on blade at different incident veloc
Station from root to tip Thrust force (T) In Newton for 12 m/s 11.2000 176967.67 18.7500 211973.95 26.0500 239803.03 32.7500 253673.46 38.6500 255596.22 43.4500 249445.88 47.0800 240457.71 49.2500 232280.04 50.0000 229502.01
esults are presented in chapter 4.6.
Fig: 3.21 Thrust force applied on blade
R
CHAPTER 4
RESULT AND ANALYSIS
4.1 Aerodynamic Analysis 4.1.1 Theoretical calculation results
4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
TSR Vs Cp
TSR
Cp
Fig: 4.1 TSR Vs Coefficient of Power (Theoretical)
5 6 7 8 9 10 11 12 130.00E+000
5.00E+005
1.00E+006
1.50E+006
2.00E+006
2.50E+006
Velocity Vs Power (W)
Velocity (m/s)
Pow
er (W
)
Fig: 4.2 Velocity Vs Power (Theoretical)
26
4.1.2 WT_Perf results
4 5 6 7 8 9 100
0.050.1
0.150.2
0.250.3
0.35
0.40.45
0.5
TSR Vs Cp
TSR
Cp
Fig: 4.3 TSR Vs Coefficient of Power (WT_Perf code)
5 6 7 8 9 10 11 12 130.00E+0002.00E+0054.00E+0056.00E+0058.00E+005
1.00E+0061.20E+0061.40E+006
1.60E+0061.80E+0062.00E+006
Velocity Vs Power (W)
Velocity (m/s)
Pow
er (W
)
Fig: 4.4 Velocity Vs Power (WT_Perf code)
27
4.1.3 GH BLADED Software Result
Fig: 4.5 TSR Vs Coefficient of Power (GH Bladed)
Fig: 4.6 Velocity Vs Power (GH Bladed)
28
4.1.4 Comparisons between Theoretical, WT_Perf, GH Bladed and Literature values of Cp and Power
4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
Comparision Theoretical,WT_Perf &GH BladedTSR Vs Cp
TheoreticalLiteratureWT_Perf [5,6]GH Bladed
TSR
Cp
[2]
Fig: 4.7 TSR Vs Coefficient of Power (Comparison)
5 6 7 8 9 10 11 12 130.00E+000
5.00E+005
1.00E+006
1.50E+006
2.00E+006
2.50E+006
3.00E+006
3.50E+006
Comparision Theoretical,WT_Perf & GH BLadedVelocity Vs Power (W)
TheoreticalLiteratureWT_Perf [5,6]GH Bladed
Velocity (m/s)
Pow
er (W
)
[2]
Fig: 4.8 Velocity Vs Power (Comparison)
29
It can be seen from the Fig 4.7 that coefficient of power increases till TSR of 7 then it gradually reduces and also from Fig 4.8 it can be seen that power production reaches maximum at wind velocity of 12 m/s after that it reduces this is because AOA of attack will be optimal at this point then the lift force will reduce giving rise to stall.
4.1.5 Comparisons between Calculated, WT_Perf, GH Bladed values of Thrust Force
4 5 6 7 8 9 100
50000
100000
150000
200000
250000
300000
350000
Comparision Theoretical, WT_Perf & GH BladeddTSR Vs Thrust Force (N)
TheoreticalWT_Perf [5,6]GH Bladed
TSR
Thru
st F
orce
(N)
Fig: 4.9 TSR Vs Thrust Force (Comparison)
4 5 6 7 8 9 100
0.2
0.4
0.6
0.8
1
1.2
Comparision Theoretical,WT_Perf & GH BladedTSR Vs Thrust Coefficient
TheoreticalWT_Perf [ Not Available]GH Bladed
TSR
Thru
st C
oeffi
cien
t
Fig: 4.10 TSR Vs Thrust Coefficient (Comparison)
30
4.2 Results of Decoupled analysis at parked condition using FLUENT
Fig: 4.11 Displacement at 50 m/s
Fig: 4.12 Displacement at 36 m/s
31
Fig: 4.13 Displacement at 60 m/s
Table: 4.1 Displacement for different Velocities
Wind Speed (m/s) Deflection of Blade (m) 36 2.507 50 3.449 60 4.766
32
4.3 Results of Decoupled analysis at parked condition Theoretical
Fig: 4.14 Displacement at 60 m/s Fig: 4.15 Von mises stress at 60 m/s
Fig: 4.16 Displacement at 50 m/s Fig: 4.17 Von mises stress at 50 m/s
33
Fig: 4.18 Displacement at 36 m/s Fig: 4.19 Von mises stress at 36 m/s
Analysis is carried out at parked condition for different wind velocities.The table 4.2 gives the details about the load applied at different wind velocities and deflection and stress distribution over blade.
Table: 4.2 Deflection and von mises stress at different velocities
Wind speed (m/s) Deflection of Blade (m) Von mises stress (MPa)
36 2.129 13.1
50 3.626 25.3
60 5.22 36.4
34
4.4 Results of FSI
Fig: 4.20 Plot of displacement at 36 m/s Fig: 4.21 Plot of Von mises at 36 m/s
Fig: 4.22 Plot of displacement at 50 m/s Fig: 4.23 Plot of Von mises at 50 m/s
35
Fig: 4.24 Plot of displacement at 60 m/s Fig: 4.25 Plot of Von mises at 60 m/s
Table: 4.3 Comparison between coupled field analysis and Decoupled analysis
Velocity m/s
Coupled field (FSI)
Decoupled analysis FLUENT
% variation
Decoupled analysis Theoretical
% variation
Displacement (m)
36 2.49 2.665 7.028 2.129 14.5
50 3.89 3.158 18.18 3.62 7.45
60 4.63 4.769 3.435 5.22 11.3
Von mises (MPa)
36 7.65 - - 13.1 41
50 14.77 - - 25.3 41.1
60 21.11 - - 36.4 42
The blade deflection during the gust condition is very high. It can be seen from the table that as wind velocity increases displacement increases. The blades are made of Graphite Epoxy and they are flexible which allow this high deflection. Percentage of variation in deflection and stress obtained from different methods is negligible.
36
4.5 Results of Decoupled analysis at operating condition using FLUENT
Fig: 4.26 Displacement at 12 m/s Fig: 4.27 von mises at 12 m/s
Fig: 4.28 Displacement at 10 m/s Fig: 4.29 von mises at 10 m/s
37
Fig: 4.30 Displacement at 8 m/s Fig: 4.31 von mises at 8 m/s
Table: 4.4 Stress and deflection at different velocity of wind.
Wind speed (m/s) Von mises (MPa) Displacement (m) 12 2.93 0.12001 10 3.04 0.10389 8 3.06 0.07379
38
4.6 Results of Decoupled analysis at operating condition Theoretical
Fig: 4.32 Displacement at 12 m/s Fig: 4.33 von mises at 12 m/s
Table: 4.5 Stress and deflection at 12 m/s of wind
Velocity in m/s Von mises (MPa) Displacement (m)
12 1.46 0.142
Table: 4.6 Comparison between Decoupled analysis FLUENT and Theoretical
Velocity (m/s) Decoupled analysis
(FLUENT)
Decoupled analysis
(Theoretical)
Displacement (m) 12 0.12001 0.142
10 0.10389 ‐
8 0.07379 ‐
Von mises (MPa) 12 2.93 1.46
10 3.04 ‐
8 3.06 ‐
The blade deflection from the analysis shows less than half a metre. This is because of the centrifugal stiffening of the blade to centrifugal force. It is observed that the maximum stress in blade is very small and is within the limit.
39
CHAPTER 5
CONCLUSION AND FUTURE SCOPE OF WORK 5.1 WORK CONCLUSION Our present study concentrates on designing a wind turbine blade of 50m radius and carry out aerodynamic analysis and also to predict the stress distribution over the blade during the operating conditions and during gust condition when the rotor blade is parked. The following observations are made.
1. Calculated value of coefficient of power, Total Power for different velocity is found to be under the Betz limit and matches the literature value [2] respectively.
2. Displacement Values of Decoupled analysis and coupled field analysis (FSI) matches with each other.
3. Displacements obtained from decoupled analysis are within the limit of literature value2.
4. Transient analysis with turbulent model (k-epsilon) model gives result close to literature values2 where it states maximum deflection is around 4 meters.
5.2 SCOPE OF FUTURE WORK 1. Analysis can be done on blade for wind turbine start-up, shut-down, Emergency-stop,
normal breaking etc can be done
2. FSI analysis under operating condition can be done. 3. 3D fluid flow analysis around the blade under parked & operating condition can be done. 4. Design can be improved to increase the overall power output by considering different
airfoils or combination of different airfoils.
5. Modal Analysis of ATOA-MIT Wind turbine can be carried out.
40
REFERENCES 1. J.F.Manwell, J.G.McGowan and A.L.Rogers, “Wind Energy Explained Theory, Design
and Application”, John Wiley and son ltd, September 2002. 2. S. Lain, B. Quintero and Y. Lopez, “Aerodynamic and Structural Evaluation of
Horizontal Axis Wind Turbines with rated power over 1 MW”. 3. Grant Ingram, “Wind Turbine Blade Analysis using the Blade Element Momentum
Method”, Version 1, Dec 13, 2005. 4. Jan van der Tempel and David-Pieter Molenaar., Wind Turbine Structural Dynamics – A Review of Principles for Modern Power Generation, Onshore and Offshore. 5. Marshall L. Buhl, Jr., Alan D. Wright, James L. Tangler, Wind Turbine design Codes: A
Preliminary Comparison of the aerodynamics. National wind technology centre,Dec 1997.
6. Ryan T. Cowgill, Jake Fouts, Byron Haleyand Chris Whitham, Wind turbine rotor design. Boise State University, College of Engineering, Dec 2006.
7. RamanandaPrabhu N, “Analysis of wind turbine blade” M.Tech thesis Manipal University June 2004-2005.
8. Lionel Anup Noronha, “EXTENDED ANALYSIS OF 300kW BLADE AND THE PRELIMINARY DESIGN OF A 500kW WIND TURBINE BLADE”, Mtech Thesis, Manipal University 2005-2006.
9. Ira H. Abbott and Albert E. Von Doennhoff, Theory of wings, Dover Publications,inc New York.Standard book number 486-60586-8, published in 1949.
10. Nian-Zhao Jiang,Xiang-Lin ma,Zhi-qing Zhang, “The Dynamic Characteristics Analysis of Rotor Blade Based on ANSYS”, May 20-22,1998.
11. Z.L.Mahri,M.S.Rouabh, “Calculation of stress using finite element method and prediction of fatigue failure for wind turbine rotor”, Seas Transactions on applied and theoretical mechanics. Issue 1, Volume 3, January 2008.
12. Chenvu zhang,Simon wang and Huimin xie,” Static structural analysis of parked composite wind turbine blades”. June 2004.
13. Mark Drela, MIT Aero & Astro,Harold Youngren, “Aerocraft, Inc,XFOIL 6.9 User Guide”,11 Jan 2001.
14. Bir G and Migliore P., “Priliminary structural Design of composite Blades for Two and Three-Blade Rotors”.
15. Rajesh Bhaskaran, Cornell University https://confluence.cornell.edu FLUENT and GAMBIT.
16. Germansheir Lloyd’s (Wind Energie).” Rules and guidelines for wind turbine design”. 17. ANSYS CFX tutorial. 18. GAMBIT and FLUENT tutorials.
41
42
PROJECT DETAILS
Student Details Student Name PRAJWAL RAO K Register Number 090922009 Section / Roll No 08 Email Address [email protected] Phone No (M) +91-9739463660 Student Name Register Number Section / Roll No Email Address Phone No (M)
Project Details Project Title DESIGN AND ANALYSIS OF HORIZNTAL AXIS WIND
TURBINE BLADE WITH 50 METER RADIUS Project Duration 11 Months Date of reporting June 21,2010
Organization Details Organization Name ATOA SCIENTIFIC TECHNOLOGY,BANGALORE Full postal address with pin code
ATOA Scientific Technologies, 198, EVOMA Business Centre, # 14, Bhattrahalli, Old Madras Road, K.R. Puram, Bangalore - 560 049, India.
Website address http://atoatech.com/
Supervisor Details Supervisor Name Dr Raj C Thiagarajan Designation MANAGING DIRECTOR Full contact address with pin code
ATOA Scientific Technologies, 198, EVOMA Business Centre, # 14, Bhattrahalli, Old Madras Road, K.R. Puram, Bangalore - 560 049, India.
Email address [email protected] Phone No (M) +91 9740 111 339
Internal Guide Details Faculty Name Dr.Satish Shenoy Full contact address with pin code
Dept of Mechanical & Manufacturing Engg, Manipal Institute of Technology, Manipal – 576 104 (Karnataka State), INDIA
Email address [email protected]