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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…………. Using the steam to make the Power !. Rotating the shaft is the ultimate goal of any power plant.

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power plant turbines

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…………..

using the steam to make the power
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.

the steam turbine
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.
slide4

Generation of Motive Power Through Newton’s Second Law

Vi

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

analysis of simple stationary impulse blade

Ve

Vi

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:

FA

FR

The force acting on the blade:

However, this force cannot develop any motive power.

slide6

Analysis of Simple Moving Impulse Blade

Vre = -Vri

Vae = Vre -U

U

Vri = Vai - U

Vai

slide7

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…

slide8

Analysis of Simple Reaction Blade

U

Vai

Vri

Vre

Vae

Change in velocity :

Motive Power Generated:

slide9

Motive Power Generated:

Thermodynamic efficiency of a Reaction blade :

A compact Reaction blade is inefficient ……Suitable for Thin fluids…

slide10

Vre

Vae

U

Vri

Vai

Simple Impulse-Reaction Blade

Jet will lose power both by Impulse and Reaction.

One important and essential element in all these cases is a nozzle.

how to provide a mass flow rate
How To Provide A Mass Flow Rate
  • Area for Flow of Fluid.
  • Proportional to the Length of the Blade.
  • More Number of Blade Spacings.
theory of turbine blading

Theory of Turbine Blading

BY

Dr. P M V Subbarao

Mechanical Engineering Department

I I T Delhi

slide14

U

Vri

Vai

Vai

Inlet Velocity Triangle

U

Vae

Vre

Exit Velocity Triangle

Vri

U

Vre

slide15

U

bi

ae

ai

be

Vai

Vae

Vri

Vre

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.

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