ON THE CONCEPT OF EFFICIENCY OF A TURBINE WITH OPEN-LOOP AIR COOLING OPERATING IN A GAS TURBINE ENGINE SYSTEM.

Three types of efficiency are examined, namely: effective (apparent), defined as the ratio of effective turbine shaft power to the available power in the primary (gas) stream; overall, defined as the ratio of effective turbine shaft power to the available power in the primary stream and in the cooling air streams; and generalized, defined as the ratio of turbine useful power, i. e. , turbine shaft power minus the power expended in compressing the coolant in the compressor, to the available power in the primary working fluid (gas) stream. The use of these coefficients in writing the power balance equation is illustrated for a turbojet engine. It is concluded that for the aircraft gas turbine engines, the overall efficiency is most convenient.