Comprehensive performance analysis and optimization of the closed Brayton cycle for waste heat recovery and cooling in hydrogen aeroengines

The Brayton cycle represents significant potential for cooling and waste heat recovery in hydrogen aeroengines. However, existing models integrating the Brayton cycle with aeroengines generally rely on hard-to-obtain thermodynamic parameters at state points (such as the turbine inlet temperature). This study proposes a modeling method that captures the coupled heat transfer among the coolant, hot-end component wall, and mainstream, making it suitable for practical hydrogen aeroengines. Five schemes-simple cycle (SC), recuperated cycle (SRC), reheating recuperated cycle (RRC), intercooling recuperated cycle (IRC), and intercooling reheating recuperated cycle (IRRC)-were evaluated based on peak wall temperature (T_max), exergy efficiency (η_exe), output power (W_net), environmental impact, heat sink requirement, economic benefits, and precooling effect. Consequently, the IRRC scheme exhibits superior overall performance, achieving an η_exe of 52.4%, a W_net of 780 kW, and an LCOE of 0.2 $/kW·h. The SC scheme has the highest cooling effect, while the SRC scheme is suitable for a limited heat sink. Moreover, sensitivity analysis of helium parameters and multi-objective optimization were conducted on the preferred IRRC scheme. Lower initial helium pressure and higher initial temperature can enhance the η_exe and W_net. The optimization of waste heat recovery shows that higher W_net is achieved by enhancing η_exe under limited heat input, with an optimal η_exe of 40%, a W_net of 710.5 kW, and a T_max of 827.6 K. Efficient waste heat recovery can offset the cost increase from the improved environmental performance. The findings are beneficial for cooling and waste heat recovery in hydrogen aeroengines.