Yeah, in turbines and jet engines, most of the compressed air is used for cooling, to keep the flame ball off of the combustion liner. PSIG leaving the last stage compressor is the same as the PSIG entering the 1st stage turbine, whats changes is the air flow rate, from the addition of the fuel. After the air hits the 1st stage turbine, then the PSIG starts dropping after each stage of gas producer turbines for jets and turbines, air flow rate stays constant, whats left over is either thrust for jets, or, for turbine engines, another set of stages of power turbines (some small turbines use the gas producer shaft for power transmission). An efficient turbine is one where the exhaust pressure is virtually ambient pressure, with high velocity airflow.
