7/30/2019 great doc6-3

1/24

Fluid Dynamic Characterization of Turbo-machinery

P M V Subbarao

Professor

Mechanical Engineering Department

Development of Measures for Solid FluidInteractions!!!

7/30/2019 great doc6-3

2/24

7/30/2019 great doc6-3

3/24

MEL346 : Syllabus

Introduction: turbomachinery / history / types /classification.

Euler equation for turbomachines.

Thermodynamics and fluid mechanics of turbomachineryMass, momentum and energy.

Radial equilibrium theory and design of blades for aturbomachine.

Design of Hydraulic turbines.

Axial flow turbines and compressors: theory and design Centrifugal compressors & Pumps

Wind Turbines

Micro Turbines

7/30/2019 great doc6-3

4/24

References

Fluid Mechanics, Thermodynamics of Turbomachinery :

S.L. Dixon.

Principles of Turbomachinery: R.K. TURTON.

Handbook of Turbomachineryedited by Earl Logan, Jr. &Ramendra Roy.

The Design of High-Efficiency Turbomachinery and Gas

TurbinesDavid G Wilson & T Korakianitis.

Principles of Turbomachinery in Air Breathing EnginesE A Baskharone.

Steam Turbines for Modern Fossil-Fuel Power Plants;

Alexander S Leyzerovich.

7/30/2019 great doc6-3

5/24

Attendance Policy

Below 80% -- one grade less.

Below 70% -- Two grades less.

Below 60% -- F Grade.

7/30/2019 great doc6-3

6/24

Fluid Dynamics of A Turbomachine

7/30/2019 great doc6-3

7/24

The Ancient Design : Undershot Water Wheel : 4000BC

7/30/2019 great doc6-3

8/24

Various Types of Modern Turbomachine

7/30/2019 great doc6-3

9/24

SOME TYPES OF WIND TURBINES: HAWT

7/30/2019 great doc6-3

10/24

SOME TYPES OF WIND TURBINES: VAWT

7/30/2019 great doc6-3

11/24

Why so many different types of either pump (compressor)

or turbine are in use ?

Is it due to (almost) infinite range of service requirements?

As a fact, for a given set of operating/resourcerequirements ,

there should be only one type of pump or turbine which is

best suited to provide best/optimum performance.

Why So Many?

7/30/2019 great doc6-3

12/24

Classification of Turbo-machines

Two main categories of turbo-machine are identified:

Firstly, those which absorbpower to increase the fluid

pressure or head (fans, compressors and pumps);

Secondly, those thatproducepower by expanding fluid to

a lower pressure or head (hydraulic, steam and gas

turbines).

7/30/2019 great doc6-3

13/24

Classification : Flow Path

7/30/2019 great doc6-3

14/24

Classification : Flow Path

Turbomachines are further categorised according to thenature of the flow path through the passages of the rotor.

When the path of the through-flow is wholly or mainlyparallel to the axis of rotation, the device is termed an axialflow turbomachine.

When the path of the through-flow is wholly or mainly in aplane perpendicular to the rotation axis, the device istermed a radial flow turbomachine.

Mixed flow turbomachines are widely used.

The term mixed flow refers to the direction of the through-flow at rotor outlet when both radial and axial velocitycomponents are present in significant amounts.

7/30/2019 great doc6-3

15/24

SolidFluid Interaction Level

Open flow

No casing or enclosure for the rotating device

Propeller is an open flow power consuming

device.Windmill is an open flow power generating

device.

Enclosed or encased flow devices

7/30/2019 great doc6-3

16/24

Further Classification of Turbomachines

Compressibility of the fluid

IncompressibleThe density is constant through the entire flow process;liquid pumps.

Compressible; Gas flows: compressors.

Impulse or reaction machines

Impulse: pressure changes are absent in the flow through the rotor. Inan impulse machine, all the pressure change take place in nozzles

Reaction: pressure changes in rotor are present.

7/30/2019 great doc6-3

17/24

7/30/2019 great doc6-3

18/24

Leonhard Euler

Leonhard Euler (1707-1783) was

arguably the greatest mathematician of

the eighteenth century.

One of the most prolific writer of all

time; his publication list of 886 papers

and books fill about 90 volumes.

Remarkably, much of this output datesfrom the last two decades of his life,

when he was totally blind.

Euler's prolific output caused a

tremendous problem of backlog: the St.

Petersburg Academy continued

publishing his work posthumously for

more than 30 years.

7/30/2019 great doc6-3

19/24

Theoretical and Rigorous Work of French

Bernoulli and Leonhard Euler.

1750:Euler offered a memoir containing analysis and

equations for hydraulic turbines.

1754: An idealized theoretical application of Newtons

Law to centrifugal impellers.

Known as Euler Equation.

Did much to help the development of hydraulic machinery. 1767: Relation between Torque and Change in moment of

momentum of the fluid as it passed through the machine.

7/30/2019 great doc6-3

20/24

Applications of Eulers Equation

Euler equation applies to all kinds of turbomachines.

Wind turbines ---- Pumps --- Gas turbines.

Axial flow machines to Radial flow to Mixed flow.

Energy extraction machinesEnergy consuming

machines.

For a turbine the value of Equation is negative.

For pumps, fans, blowers and compressors it is positive.

h S i i f

7/30/2019 great doc6-3

21/24

The Superiority of Vector Parameters

kVjViVVzr

7/30/2019 great doc6-3

22/24

Eulers Work Equation

Torque exerted by flow on blade row = shaft output torque

= Rate of change of Angular momentum of fluid = t

Euler Theory:

kVjViVV zr

7/30/2019 great doc6-3

23/24

Define, L as Angular momentum

Angular momentum is moment of linear momentum of

angular velocity, V

For a steady flow through a turbomachine:

Inlet rate of angular momentum :

7/30/2019 great doc6-3

24/24

Exit rate of angular momentum at exit:

Change in Rate of angular momentum: