turbo machinery-lecture 1
TRANSCRIPT
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013
Mechanical Engineering Department MENG05H03
MENG05H03 Module Specifications
by
Prof. Osama Ezzat Abdellatif
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
The most common practical engineering application for fluid mechanics is the
design of fluid machinery. Hence, the purpose of this module is to provide you
as mechanical engineers with further in-depth knowledge on applying energy
transfer
considerations in design of
pumps,compressors,
turbines.
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
knowledge and understanding
On completion of this moduleYOU should be able to
demonstrate knowledge and understanding of
1. application of scientific principles of fluid dynamics,
engineering thermodynamics and heat transfer;
Subject-specific cognitive skills
On completion of this module theYOU should be able to:
2. apply basic scientific principles of fluid dynamics, engineering thermodynamics andheat transfer in design functions;
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
Subject-specific practical skills
On completion of this moduleYOU should be able to
Demonstrate ability in:
3. use vector triangles to determine and evaluate
enginecomponent performance;
4. use standard laboratory aerodynamicequipment to generate fluid machineryperformance data;
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
Key/transferable skills
On completion of this moduleYOU should be able to
demonstrate ability in:
5. use available data and search necessary data
and apply
it to conduct calculations and presentinnovative solutions
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
Module Code: MENG05H03, Modular Weight: 10
Lecture: 24, 1 hr lectures, Sunday 09-11, Room: 309
Tutorials: 24, 1 hr tutorials, Sunday, 11:13, Room: 309
Assessment: -
- A 120 minute written & unseen final exam. This method
carries 70% of the total mark and assesses learning outcomes
1, 2, 3, 5.
- Two-classwork, two-homework assignments, andterm/group projects to be submitted on the 4th, 8th, and 11thweeks. This method carries 30% of the total mark andassesses learning outcomes 2, 3,4.
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
- Energy transfer considerations.
- Fluid dynamics of fluid machinery.
- Classification of fluid machinery.
- Theory and design of pumps, turbines,and compressors.
- Performance characteristics and scaling/similaritylaws-a practical application of dimensional analysis.
- Selection criteria and operating systems.
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British University in Egypt (BUE) Fluid Machinery
Faculty of Engineering 4th year, 2012/2013Mechanical Engineering Department MENG05H03
1. S. M. Yahya, Turbines, Compressors and Fans,Tata McGraw-Hill,2005.
2. T. Wright, FluidMachinery: performance, analysis, and design,
CRC Press LLC, 1999.
3. B. K. Hodge, Alternative Energy Systems, John Wiley & Sons;
2009.
4. Yunus A. Cengel and John M. Cimbala, FluidMechanics: Fundamentals and Applications, NY
McGraw-Hill, 2007.
5. R.K. TURTON Principles of TurbomachinerySpringer 1994.
6. J. E. Logan, & R. Ramendra, andbook of Turbomachinery, Roy.CRC Press 2003
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No. Date Title
01 10.02.13 Introduction to fluid machinery
02 17.02.13 Flow similarity and dimensional analysis
03 24.02.13Pumps :
Part I: Definitions and classifications, basic equationsapplied to centerigual pumps, velocity triangles,
and characterist curves.
04 03.03.13 Part II: Basic equations applied to axial flow pumps or
propeller pumps, velocity triangles and analysis,
system characteristics.
Department of Mechanical Engineering
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No. Date Title
05 10.03.13 Part III: Pumps in series and in parallel, affinty laws(head
relation, discharge relation, power relation and
specific speed), losses and cavitation in pumps.
Turbines :
06 17.03.13 Part I: Basic definitions, hydraulic analysis, dimensionless
parameters and turbines classifications.
07 24.03.13 Part II: Implus (Pelton wheel) versus reaction (Francis and
Kaplan) turbines; analysis of forces and power
generation.
08 31.03.13 Part III: Turbines performance and hydro-electric plants.
Department of Mechanical Engineering
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No. Date Title
Compressors :
09 07.04.13 Part I:Axial flow compressors; velocity diagrams, power
input factor, compressor characteristics
10 14.04.13 Part II: Radial flow compressors; velocity diagrams, degree
of reaction, compressor characteristics
Part III: Fans and Blowers.
11 21.04.13 Working principle, velocity triangles and parametriccalculations: work, efficiency, nubmer of
Impeller size.blades and
12 28.04.13 Revision week
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Outline
Course layout and time shedule
Summary ofbasic equations of motion
Classification of fluid machinery
Terminologies
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Energy transfer considerations Summarizing the basic equations of motion;
conservation of mass, momentum, and energy.
Identifying the various types of fluid machinery;
pumps, turbines, and compressors.
Terminologies
Literature
Lecture # 1
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What do we expect to have?
Mechanical devices, engineering systems and flow physics.
What are the rquirements?Good knowledge of fluid dynamics, thermodynamics, and
heat transfer.
Equations are to be used, however, simplifications are to bemade in order to arrive at simple and understandable relations
that well describe fluid machinery operation and performance.
Applications:
- Ground and space vehicles, - Turbomachinery industry,
- Marien applications, - Petrolum industry,
- Environmental and domestic engineering.
Energy Transfer Considerations
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When dealing with engineering problems, it is desirable to obtain fast
and accurate solutions at minimal cost. Most engineering problems,including those associated with fluid flow, can be analyzed using one
of three basic approaches:
- Differential,
- Experimental,- Control volume/Integeral.
The finite control volume approach is remarkably fast, simple
and usually gives answers that are sufficiently accurate for most
engineering purposes. Therefore, despite the approximations
involved, the basic finite control volume analysis performed with a
paper and pencil has always been an indispensable tool for
engineers.
Basic Flow Analysis Techniques
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Integral versus Differential Analysis
The control volume technique, or integral forms of equations
are usually useful for determining overall features of flow.
However, we cannot obtain detailed knowledge about the flow
field inside the CV motivation for differential analysis.
Integral Differential
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The mass of a differential fluid element dVwithin
the control volume (CV) is dm = dV. The total
mass within the CV at any instant in time t isdetermined by integration.
Conservation of Mass/Continuity Equation
Tensor Form :
Cylindrical Form :
0)()()(
z
C
y
C
x
C
t
Zyx
ou tin
mm dVt
CV
Rate of change of masswithin the CV:
C
0)(
C
t
Vector Form :
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00)(
A
N
VVV
dACdVt
dVCdVt
Conservation of Mass/Continuity Equation
Rate of Change of Mass within the CV :
For Steady Flow :
222111
22
0
ACAC
dACdACdAC
NN
A
N
A
N
A
N
Vector Form : 0)(
C
t
AV
dAnCdVC )()( Gausss Divergence Theorem :
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Department of Mechanical Engineering
Conservation of Momentum
FDt
VDdzdydxam
Dt
VDm
Where:
surfacebody FFF
ForceViscousForcePressure
3,2,1,
surface
ibody
F
idzdydxgF
Momentum is a conserved quantity, and is defined as the productof the mass and velocity of an object (L= mv). Momentum is either
linearor angular. Both the linear and the angular momentums are
vector quantities, since they have directions as well as magnitudes.
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Department of Mechanical Engineering
Consevation of Linear Momentum
Neglecting body forces, C2 & C1 are uniform, and for steady flow :1
)( 1211
12
2
2 CCmFmdCmdCFAA
s
Considering pressure forces as not part of the surface/external forces :
)()( 111222 CmAPCmAPFF ext
Navier-Stokes Equation
s
V
n
AV
FdVFdACCdVCt
F = external/body force/kgFs= surface force
P. Force, B. Force, V. Force
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Department of Mechanical Engineering
Conservation of Angular Momentum
Angular momentum : The angular momentum, L, is a vector
conserved quantity. If r and v are then the magnitude of theangular momentum with respect to point Q is given by L = m v r.
The SI unit for angular momentum
is the kgm2 / s. A spinning objecthas angular has an angular
momentum, L. The more it has, the
harder is to stop it from spinning.
Q
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Department of Mechanical Engineering
In many situations, steady flow and uniform velocities might beconsidered, hence the theorem of angular momentum can be written as:
)( 1122 rCrCmFrT uu
)()( 11221122 UCUCmrCrCmTP uuuu
where r is the radius vector from the fixed point to the point of application
of F. The mechanical power:
)( 1122 UCUCw uu The specific work/the Euler turbine equation:
Conservation of Angular Momentum
momentumangularofratenet
A
u
momentumangularofchangeofratetimeV
u
torquesexternalallofSum
dACCrdVCrt
T )()()()(
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Department of Mechanical Engineering
The Head Form (Energy/unit weight)
Elevation
Head
Velocity
Head
.2
2
constzg
Vp
Press.
Head
The Bernoulli equation can be written with terms in
head dimension [m]
The Bernoulli Equation
The sum of the flow, kinetic, and potential, energies of afluid particle is constant along a streamline during steady
flow when the compressibility and frictional effects are
negligible
The Conservation of Energy
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Department of Mechanical Engineering
CVtheondoneworkofrateCVthetotransferheatenergytotalofChange
WQEd
Steady State Work/Flow Applications :
The First Law of Thermodynamics
A change of the total energy (internal, and kinetic, potential) is
equal to the rate of work done on the control mass plus the heat
transfer to the control mass.
Between Two States 1 & 2: 212112 WQEE
2121
1
2
2
2
212112
2
1
2
1WQmgzmVUmgzmVU
WQEPKEUEPKEU
CVCVininoutout WQmzVhmzVh
22
2
1
2
1
pvuh
where
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Department of Mechanical Engineering
As shown in figure below, a fixed vane turns a water jet of areaA
through an angle without changing its velocity magnitude. The flow is
steady, frictionless, and pressure is atmospheric everywhere.
(a) Find the components Fxand Fyof the applied vane force.
(b) Find expressions for the force magnitude F and the angle
between F and the horizontal; plot them versus .
Example I
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Department of Mechanical Engineering
The control volume has only one dimensional inlets and outlets,
then
iniioutii VmVmF )()(
The force magnitude is
Example I
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Department of Mechanical Engineering
Energy addedto fluid Energy extractedfrom fluid
Pumps, fans, compressors
Cased (Radial, Mixed flow, Axial)
Uncased (Screws, Propellers)
Positive displacement machines
Reciprocating
- Direct driven, Crank driven, Swashplate.
Rotary
- Screw, Gear, Vane.
Turbines
Reaction
Windmills
Pelton wheel
Radial: Pelton
Mixed: Francis
Axial :Kaplan
Rotodynamic Impulse
Classification of Fluid Machines
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Department of Mechanical Engineering
Fluid Statics: It is the branch of science that is mainly concerned withfluids at rest (hydro/aero statics).
Fluid Kinematics: It is the branch of fluid science describing the motion offluids without considering the forces and moments that cause the motion.
Fluid Dynamics: It is the branch of science that is mainly concerned with
fluids in motion (hydro or gas/air dynamics) studying forces and theresulting motion of objects through liquids/non-liquids.
Thermodynamics: It is the science of energy conversion involving heatand other forms of energy, most notably mechanical work. It studies and
interrelates the macroscopic variables, such as temperature, volume, andpressure, which describe any physical thermodynamic system.
Heat Transfer: It is a discipline of thermal engineering that concerns thetransfer of thermal energy from one physical system to another.
Terminolgies
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Department of Mechanical Engineering
Velocity profile: The spatial variation in a velocity component or vector
through a region of a fluid flow. For example, blades inlet and exit velocityprofiles generally defines the variation in axial/radial velocity with radius along
flow passage. The velocity profile is part of a velocity field.
No-slip condition: The requirement that at the interface between a fluid anda solid surface, the fluid velocity and surface velocity are equal. Thus if the
surface is fixed, the fluid must obey the boundary conditionthat fluid velocity = 0at the surface.
Incompressible flow: A fluid flow where variations in density are sufficientlysmall to be negligible. Flows are generally incompressible either because the
fluid is incompressible (liquids) or because the Mach number is low (roughly 0 or
Pgage < 0 is simply the pressure above or below atmospheric pressure.
Manometer: A device that measures pressure based on hydrostatic pressureprinciples in liquids.
Terminolgies
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Department of Mechanical Engineering
Friction drag: The part of the drag on an object resulting from integratedsurface shear stressin the direction of flow relative to the object.
Pressure (or form) drag: The part of the drag on an object resulting fromintegrated surface pressure in the direction of flow relative to the object. Larger
pressure on the front of a moving bluff body(such as a car) relative to the rear
results from massive flow separation and wake formation at the rear.
Induced drag: The component of the drag force on a finite-span wing that isinduced by lift and associated with the tip vortices that form at the tips of the
wing and downwash behind the wing.
Wake: The friction-dominated region behind a body formed by surfaceboundary layers that are swept to the rear by the free-stream velocity. Wakes
are characterized by high shearwith the lowest velocities in the center of thewake and highest velocities at the edges. Frictional force, viscous stress, and
vorticity are significant in wakes.
Terminolgies
Lit t
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Literature
1. S. M. Yahya, Turbines, Compressors and Fans, Tata McGraw-Hill,
3rd Edition, 2005.
2. T. Wright, Fluid Machinery: performance, analysis, and design,
CRC Press LLC, 1999.
3. B. K. Hodge, Alternative Energy Systems, John Wiley & Sons;
April 2009.
4. Yunus A. Cengel and John M. Cimbala, Fluid Mechanics:
Fundamentals and Applications, NY McGraw-Hill, 2007.
5. R. K. Turton, Principles of Turbomachinery, Second EditionSpringer 1994, ISBN: 0412602105
6. J. E. Logan, & R. Ramendra, Handbook of Turbomachinery, Roy.
CRC Press 2003, ISBN: 978-0-8247-0995-2.