Open Gas Turbine Cycle

Open gas turbine cycle is the most basic gas turbine unit. The working fluid does not circulate through the system, therefore it is not a true cycle. It consists of a compressor, a combustion chamber and a gas turbine. The compressor and the gas turbine are mounted on the same shaft. The compressor unit is either centrifugal or axial flow type. The working fluid goes through the following processes:

1-2 irreversible but approximately adiabatic compression
2-3 constant pressure heat supply in the combustion chamber
3-4 irreversible but approximately adiabatic expansion of combustion gases

In the simplified T-s diagram, shown above, pressure loss at compressor inlet, in combustion chamber and at turbine outlet are neglected. Thermal efficiency of the cycle is: