A Brief Introduction About Gas Turbine Plant

Gas Turbines are one of the most efficient equipment for 

converting fuel energy to mechanical energy.

The three main

sections of a Gas Turbine are the Compressor, Combustor and Turbine. The gas turbine power plant has to work

  

continuously for long period of time without output and

 performance decline. Apart from the main sections there are

 other important Auxiliaries systems which are required for 

operating a Gas Turbine Power Plant on a long term basis

.

Gas turbine engines derive their power from burning fuel in 

a combustion chamber and using the fast flowing 

combustion gases to drive a turbine in much the same way 

as the high pressure steam drives a steam turbine.

One major difference however is that the gas turbine has a

 second turbine acting as an air compressor mounted on the

 same shaft. The air turbine (compressor) draws in air, 

compresses it and feeds it at high pressure into the

 combustion chamber increasing the intensity of the burning flame.

It is a positive feedback mechanism

As the gas turbine speeds up, it also causes the compressor 

to speed up forcing more air through the combustion 

chamber which in turn increases the burn rate of the fuel 

sending more high pressure hot gases into the gas turbine 

increasing its speed even more. Uncontrolled runaway is 

prevented by controls on the fuel supply line which limit the

 amount of fuel fed to the turbine thus limiting its speed.

              

 simple diagram of gas power plant cycle.

CLASSIFICATION OF GAS TURBINE:-

1-  Constant pressure combustion gas turbine

(a) Open cycle constant pressure gas turbine.

(b) closed cycle constant pressure gas turbine

2-Constant volume combustion gas turbine.

Operation of gas turbine.

 1- STARTING

2- Shut Down.

 1- Starting of gas turbine.

 Starting of gas turbine power plant require an auxiliary 

power source , till the plant own compressor inducts air and 

compresses it to a pressure such that expansion from 

 resosnalbale temperature will develop enough power to

 sustain operation . the stater may be 

1 - Internal combustion engine.

2- A steam turbine.

3- An Auxiliary electric motor 

4- Another gas turbine.

  It Must be coupled to the turbo - compressor shaft with a

 disengaging or over - running clutch.

 A main generator or its direct connected exciter may be 

pressed into temporary service as a motor.

 STARTING PROCEDURE:-

 1 Run the unit and induct the air,

2- Actuate the combustion ignition system and inject the  

    fuel .

  The fuel is controlled to obtain the necessary warm up

.

3-  Adjust the speed and voltage and synchronize the alternator.

4- Build up the load on the alternately governed gear control;

 SHUNT DOWN F OF GAS TURBINE:-

 Shunt down of gas turbine occur very quickly after the fuel is

 cuts of from the combustor. A  Rapid shunt down is desirable

since it minimizes the "chilling" effect resulting from passing

 cold air through the hot turbine. Turning gears are usually 

employed , or alternating the starting device may be operated

 at reduced speed to ensure symmetrical of rotor.

 This avoids thermal " kinking of the shaft.

 Gas turbine fuel used:-

various types of fuel are used in gas power turbine.

1- Gaseous Fuels.( Natural gas)

2- Liquid Fuels. ( Liquid fuels of petroleum.)

3- Solid Fuels.(such as coal)

Advantage of gas turbine power plant over thermal power plants:-

1. No ash handling problem.
2. Low capital cost
3. the gas turbine plants can be installed at selected load center as space requirement is less where steam power plants can not accommodated.
4. fewer auxiliaries used
5. gas turbine can built quickly.
6. economical as thermal power plant in components.
7. storage of fuel is much smaller and handling is easy

APPLICATION OF GAS TURBINE POWER PLANTS.

1. To Drive generators and supply peak load in steam , diesel or hydro plants.
2. To work as combination plants with conventional steam boilers.
3. To supply mechanical drive fr auxiliaries.