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 (p_C,out), and CO₂ mass flow rate (m_c) are analyzed to evaluate the performance of regenerative cooling, the Reg. CBC, and the Rec. CBC TCS. Indicators such as thermal efficiency (η_th), net output power (P_net), cooling fuel mass flow rate (m_fc), minimum CO₂ mass flow rate (m_c,min), maximum wall temperature (T_w,max), and total weight (W_t) are assessed. Results show that, at the same p_C,out, the Rec. CBC is greater than the Reg. CBC in terms of m_c,min, η_th, P_net, and W_t, requiring a lower m_fc. 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 p_C,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 p_C,out.