gas turbine working principle

working principle of gas turbine power plant :

in a gas turbine first air is obtained from the atmosphere and compressed in an air compressor. this high prsuure air is then pased into the combustion chamber, where it is heated due to combustion of fuel. The product of combustion(hot gases) of high pressure and temperature passes through the passages formed by the stationary and rotating blades of gas turbine. Ajet of hot gases is made to flow over ring of blades imparting rotary motion to the shaft of turbine. A large part of power developed by the turbine rotor is consumed for a driving a compressor which supplies air under pressure of combustion chamber, while remaining power is utilized for doing the external work.

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. A simple gas turbine is comprised of three main sections a compressor, a combustor, and a power turbine. The gas-turbine operates on the principle of the Brayton cycle, where compressed air is mixed with fuel, and burned under constant pressure conditions. The resulting hot gas is allowed to expand through a turbine to perform work.

In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and heat rejection. Together, these make up the Brayton cycle.

In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor). Heat is added in the combustion chamber and the specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection.

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