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Power Plant Turbines PowerPoint PPT Presentation


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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

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Power plant turbines l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

Analysis of Simple Moving Impulse Blade

Vre = -Vri

Vae = Vre -U

U

Vri = Vai - U

Vai


Slide7 l.jpg

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 l.jpg

Analysis of Simple Reaction Blade

U

Vai

Vri

Vre

Vae

Change in velocity :

Motive Power Generated:


Slide9 l.jpg

Motive Power Generated:

Thermodynamic efficiency of a Reaction blade :

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


Slide10 l.jpg

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 l.jpg

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 l.jpg

Theory of Turbine Blading

BY

Dr. P M V Subbarao

Mechanical Engineering Department

I I T Delhi


Slide14 l.jpg

U

Vri

Vai

Vai

Inlet Velocity Triangle

U

Vae

Vre

Exit Velocity Triangle

Vri

U

Vre


Slide15 l.jpg

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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