Performance analysis of cooling system based on improved supercritical CO2 Brayton cycle for scramjet

•The SCO2 cycle for the scramjet cooling application has been developed.•The heat transfer performance of the SCO2 in the engine wall channels is analyzed.•Two improved cycle layouts are proposed.•The selection criteria for different cooling requirements are developed. The cooling of scramjet is a critical issue for the hypersonic vehicle, but the conventional regenerative cooling system cannot satisfy the cooling requirement and the fuel consumption for cooling will exceed the flow rate for combustion at high Mach number. To reduce the hydrocarbon fuel flow rate for cooling, the supercritical carbon dioxide (stated as SCO2) cycle for the scramjet cooling application has been proposed in this paper. Firstly, the recompression SCO2 is analyzed as the based cycle. A model of the recompression SCO2 cycle cooling system tailored for scramjet is established considering the heat absorbing process. However, the results show that the fuel consumption for cooling increases rather than decreases compared with the regenerative cooling system. Then two improved cycle layouts are proposed. The fuel consumption for cooling can reduce by 28.8% and the corresponding power output is 159.5 kW. Besides, comparisons between the two improved cycles are made and the selection criteria for different cooling requirements are developed. The results indicate that it is better to choose a larger split ratio to acquire higher power output for improved cycle 1. As for improved cycle 2, a smaller split ratio should be selected to reduce the system weight.