Thermodynamic design and optimization of the multi-branch closed Brayton cycle based precooling-compression system for a novel hypersonic aeroengine

Fuel indirect precooled engines are promising power for next generation in- and trans-atmospheric vehicles. As reported, performance of the engine family depends ultimately on sophisticated flow path arrangement of the multi-branch tandem cooling-compression (TCC) system, and for which the design criteria have not been well established. On account of this, a generalized model engine is developed and used to derive and evaluate the optimum configurations of the engine family. The results indicate that intake air temperature can be cooled to 120–350 K by heat capacity rates (HCRs) matched single-branch design for Mach 5 flight condition, with the corresponding air pressure ratio is around 74–110. However, under the constraints induced unmatched condition of HCRs, the precooling and compression effect for air can be degenerated by an order of magnitude. Contrarily, the multi-branch design exhibits excellent performance adaptability even though the overall HCRs are unmatched, with the minimum precooling temperature and maximum pressure ratio of air can be obtained when system branch number is equal to the overall HCR of regenerator. Through the evaluation of the SABRE-4 and Scimitar configurations, it shows that performance of the multi-branch system can be further improved by introducing the fuel expansion and recooling scheme.