1. Mechanical Engineering Department
Power Plant Turbines
P M V Subbarao
Associate Professor
Mechanical Engineering Department
I I T Delhi
A Techno-economically feasible model for large Power Plants…………..

2. Using the steam to make the Power !
Rotating the shaft is the ultimate goal of any power plant.
As you have probably noticed, from the text and pictures on Steam Generators, there is no shaft.
Which leads to the question:
"now that you have all this super energized steam or Gas, how do you get work from it ? "
A boilers / Combustor is only one part of a larger operation, granted, it's a large part but most important part of the operation is it's ability to apply all this steam power.

3. The Steam Turbine
The more modern method of extracting mechanical energy from thermal energy is the steam turbine.
Steam turbines have been the norm in various land based power plants for many years.
Motive power in a steam turbine is obtained by the rate of change in momentum of a jet of steam impinging on a curved blade which is free to rotate.
The steam is (partially or fully) expanded in a nozzle, resulting in the emission of a high/medium/low velocity jet.
This jet of steam impinges on the moving vanes or blades, mounted on a shaft.
Here it undergoes a change of direction and/or magnitude of motion which gives rise to a change in momentum and therefore a force.

4. Generation of Motive Power Through Newton’s Second LawVi U
Freaction Ve
Work is said to be done by a system iff
The sole effect external to the system
can be reduced to raising of weight

5. Analysis of Simple Stationary Impulse Blade
Consider a stationary 180 degree curved blade.
A jet with a velocity Vi incidence on the blade.
The blade deflects the jet along its surface and finally the jet leaves with a velocity Ve.
The magnitude of velocity vector remains unchanged.
However, the direction changes through 180 degrees.
Ve = - Vi
The change in velocity : - 2 Vi.
A jet with a finite mass flow rate will experience a rate of change of momentum, FA: Vi Ve FA FR
The force acting on the blade:
However, this force cannot develop any motive power.

6. Analysis of Simple Moving Impulse Blade
Vre = -Vri
Vae = Vre -U U
Vri = Vai - U
Vai

7. Kinetic power lost by the jet :
Power lost by jet = Power gained by the Blade
Initial Power of the jet :
Thermodynamic efficiency of an impulse blade :
An efficient impulse blade is bulky …… Suitable for Dense fluids…

8. Analysis of Simple Reaction Blade
Vai
Vri
Vre
Vae U
Change in velocity :
Motive Power Generated:

9. Motive Power Generated:
Thermodynamic efficiency of a Reaction blade :
A compact Reaction blade is inefficient ……Suitable for Thin fluids…

10. Simple Impulse-Reaction Blade
Vai
Vae
Vri
Vre U
Jet will lose power both by Impulse and Reaction.
One important and essential element in all these cases is a nozzle.

11. How To Provide A Mass Flow Rate
Area for Flow of Fluid.
Proportional to the Length of the Blade.
More Number of Blade Spacings.

12. Theory of Turbine BladingBY
Dr. P M V Subbarao
Mechanical Engineering Department
I I T Delhi

14. U
Vri
Vai
Inlet Velocity Triangle
Vai
Vri U U
Vre
Vae
Exit Velocity Triangle
Vre

15. U
Vri
Vai
Vre
Vae bi ai ae be
Vai: Inlet Absolute Velocity
Vri: Inlet Relative Velocity
Vre: Exit Relative Velocity
Vae:Exit Absolute Velocity
ai: Inlet Nozzle Angle.
bi: Inlet Blade Angle.
be: Exit Blade Angle.
ai: Exit Nozzle Angle.