engineering thermodynamic steam and gas turbine power plant

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 a 33% efficient gas-turbine approximately two / thirds of this work is spent compressing the air, the rest is available for other work

download more at
http://www.freestudy.co.uk/thermodynamics/t9109.pdf

at this link you will also can see some thermodynamic calculation for steam and gas turbine.