Performance evaluation of regenerative cooling and closed Brayton cycle for hypersonic vehicles

This study develops a one-dimensional model for regenerative cooling and SCO2 regenerative closed Brayton cycle (Reg. CBC) and recompression CBC (Rec. CBC) thermoelectric conversion systems (TCS) to address thermal protection for scramjet combustion chamber walls and power supply for hypersonic vehicles. Under typical heat flux distribution at Ma = 6, key parameters such as the cooling fuel inlet temperature, compressor outlet pressure (pC,out), and CO2 mass flow rate (mc) are analyzed to evaluate the performance of regenerative cooling, the Reg. CBC, and the Rec. CBC TCS. Indicators such as thermal efficiency (ηth), net output power (Pnet), cooling fuel mass flow rate (mfc), minimum CO2 mass flow rate (mc,min), maximum wall temperature (Tw,max), and total weight (Wt) are assessed. Results show that, at the same pC,out, the Rec. CBC is greater than the Reg. CBC in terms of mc,min, ηth, Pnet, and Wt, requiring a lower mfc. For short flight durations, regenerative cooling with storage batteries results in the lightest weight, while for medium flight durations, the CBC is the lightest. For long flight durations, regenerative cooling with fuel cells is the lightest. As pC,out increases, the time span of the weight advantage of SCO2 CBC grows, with the Rec. CBC shows a longer advantage than the Reg. CBC at the same pC,out.