Performance analysis of multi turbines and SOFC combined power generation system for hypersonic vehicles

Scramjets are one of the most promising propulsion systems for hypersonic vehicles, but their application in vehicles with long-endurance is limited by electricity supply issue. This study proposes a combined power generation system based on solid oxide fuel cells and turbines for efficient power generation and energy cascade utilization. A lumped parameter model coupling proposed system and scramjet is developed for performance evaluation. Results indicate that in the process of energy cascade utilization, more pressure energy is utilized by turbines rather than fuel cells could enhance the electric power, and the system under the optimal energy cascade utilization condition obtain 537.13 kW of electric power and maintain the efficiency of fuel cells at 56.79 %. Further, for the system under optimal energy cascade utilization, there exists an optimal fuel utilization ratio of the fuel cells (0.7) which maximizes the electric power (539.37 kW), and the system electric power increases with decreasing current density of the fuel cells. Finally, the effect of power generation on propulsion is not significant. The maximum decrease in specific thrust and specific impulse is less than 0.4 % and 0.8 % per 100 kW power generation respectively. This research provides a novel scheme to achieve power generation for hypersonic vehicles.