An Investigation of Cooled Cooling Air for a Mach 2.2 Commercial Supersonic Transport

One of the many challenges faced in the development of gas-turbine propulsion systems for high-speed flight is the increase in the total temperature of the flow entering the engine. This results in higher compressor exit and turbine entrance temperatures which in turn require increased cooling flows that negatively impact cycle efficiency, engine size, and ultimately aircraft fuel burn. The use of a heat exchanger to cool the compressor bleed air, called cooled-cooling air, has been proposed as an enabling technology to reduce turbine cooling requirements. This paper describes the initial model development and evaluation of a fuel-air cooled-cooling air system on the fuel burn for a Mach 2.2 commercial supersonic transport designed to carry 55 passengers for 4500 nmi. For the assumptions made, there was a modest decrease of fuel of about 1000 lbs. relative to the baseline design, although this is likely a conservative result. Another finding was that the choice of overall pressure ratio and throttle ratio greatly influence the impact that CCA has.