turbo machinery-lecture 1

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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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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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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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Subject-specific practical skills


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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Key/transferable skills


demonstrate ability in:

5. use available data and search necessary data

and apply

it to conduct calculations and presentinnovative solutions


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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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- 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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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.



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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


12/34Department of Mechanical Engineering

Outline

Course layout and time shedule

Summary ofbasic equations of motion

Classification of fluid machinery

Terminologies



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



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



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



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



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 :



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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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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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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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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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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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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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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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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The control volume has only one dimensional inlets and outlets,

then

iniioutii VmVmF )()(

The force magnitude is

Example I


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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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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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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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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.

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