Consider two versions of a jet engine. The first is a standard engine run with a turbine inlet temperature of 1200 K. The second is identical, except that its turbine is cooled by bleeding air from the compressor; in this way, the allowable turbine inlet temperature may be raised to 1600 K. To make an estimate of the effect of this modification on the thrust, suppose that the engine is flying at Mach 2 at an altitude where the ambient temperature is 200 K and that compressor pressure ratio is 9:1. Suppose also that for the second engine 10%
of the airflow is bled from the compressor at a point where the pressure ratio is 9:1. After, cooling the turbine, the bleed air is exhausted from the engine with no appreciable velocity. For simplicity assume all components of both engines to be reversible. Let γ = 1.4 and cp = 1.0 kJ/(kg • K).
(a) Determine the thrust of the two engines per unit mass ow of air entering the compressor.
(b) What is the ratio of the thrust specific fuel consumption of the second engine to that of the first?