In gas turbine power plant (GTPP) the fuel (Gas & Oil) is combusted in a combustion chamber in combination with the compressed air. The hot gases of combustion at a high pressure are used to rotate the gas turbine. The gas turbine is coupled with electric generator.
Uses of GTPS
Gas turbine plants have the following application.
- For supplying peak loads with other power plants.
- To work in combination with text-tile industry (Combined cycle power station).
- To supply mechanical drive for auxiliaries.
Advantages of Gas Turbine Power Plant
The gas turbine power station has the following advantages as compared with other power plants.
- The GTPP is quick starting usually it takes two or three minutes.
- The GTPP requires very less amount of water only for cooling.
- It requires very less space as compared to other power plants.
- Its installation time is very less.
- It require less operation staff
- Due to quick starting and picking up load it can be used as peak load plants.
- It can be used to restore the grid system after total fail-over.
- Very heavy foundation are not required for installation.
- Problem of coil and ash handling is illuminated.
- It can be installed at the end of transmission line to be used as synchronous condenser to improve voltage and power factor.
Working of Gas Turbine Power Plant
A simple gas turbine plant consist of compressor combustion chamber, gas turbine and generator. When the unit runs atmospheric air is drawn in by the compressor which rises its pressure to about 17 to 20 times that of atmospheric pressure.
The fuel injected in the combustion chamber and it buns in the combustion chamber. These high pressurized and temperature gases from the combustion are passed through the gas turbine, where the gas expend and gives its motive power to run the turbine rotor. Part to he power develop by the turbine is used to run the compressor and electrical generator.
Thus the mechanical energy is converted tin to electrical energy. After expansion the gases leave the turbine at the atmospheric pressure is brought down from 1600C to 650c. In gas power turbine station above 65% of power is used to drive the compressor and only 25% of power is used for electric generation.
Parts of GTPP
The main component of GTPP are as follows.
- Air Compressor
- Combustion chamber
- Gas Turbine
- Speed Control gears
- Starting mechanize
The air is sucked from the atmosphere and compressed by the air compressor and this pressurized air is coupled to the same shaft as that of the turbine and the compressor is run by the power of the turbine.
In Combustion chamber the compressed air is mixed with the fuel(gas & liquid) at high pressure and hot gases from the combustion chamber is directed to the gas turbine to rotate.
The gas turbine consist of several fixed and moving blades. The hot gases are applied to the turbine which increases the speed of turbine so mechanically energy produced in the turbine.
The generator used with GTPP is normally the same characteristic as that use with the other types of power plants.
Speed Control Gears
The speed of the gas turbine is normally very high (4850 to 5500 rpm). The speed is reduced to normally 3000 rpm with 50 c/s frequency system and for 60 c/s frequency speed is reduced to 3600 rpm. For this purpose special speed reduction gears are used with GTPP.
The gas turbine is not self starting and needs to bring it to the self starting a diesel engine or electric motor is used with the gas turbine.
Open Cycle System
In open cycle system the fresh atmospheric air is drawn in by the compressor its pressure is raised and heat is added in the combustion chamber. The hot gases from turbine where they expend to do the mechanical work. The bot gases after passing through the turbine or exhausted into the atmosphere. The majority of GTPP are of open cycle type.
Closed Cycle System
In closed cycle system the air is compressed by the compressor. This compressed air is burned in combustion chamber from the combustion chamber the hot gases are feed to gas turbine. Where it is expended after passing through the turbine the exhaust gas is cooled to the original temperature in the re-cooler (condenser) then it re-enters to the compressor to begin the cycle.