Open and closed cycle gas turbine power plant

Construction and working principle of Open cycle gas turbine power plant

In the open cycle gas turbine, air is drawn into the compressor from atmosphere and is compressed. The compressed air is heated by directly burning the fuel in the air at constant pressure in the combustion chamber. Then the high pressure hot gases expand in the turbine and mechanical power is developed.

Part of the power developed by the turbine (about 66%) is used for driving the compressor. The remaining is available as useful output. The working fluid, air and fuel, must be replaced continuously as they are exhausted into the atmosphere. Thus the entire flow comes from the atmosphere and is returned to the atmosphere.

Construction and working principle of closed cycle gas turbine power plant

In this, the compressed air from the compressor is heated in a heat exchanger (air heater) by some external source of heat (coal or oil) at constant pressure. Then the high pressure hot gases expand passing through the turbine and mechanical power is developed. The exhaust gas is then cooled to its original temperature in a cooler before passing into the compressor again.

The main difference between the open and closed cycles is that the working fluid is continuously replaced in open cycle whereas it is used again and again in a closed cycle. The open cycle plant is much lighter than the closed cycle. Hence it is widely used.