Thermodynamics analysis of a turbojet engine integrated with a fuel cell and steam injection for high-speed flight

The high-speed flight can be achieved by high-performance aero-engines. A traditional turbojet engine with steam injection is hardly operated at Mach 3.5–5 owing to the low specific impulse. The performance of turbine-less jet engines is outstanding. No turbines exist in the engine and compressors are powered by fuel cells. Therefore, the limitation of the highest combustion temperature caused by turbines disappears. In addition, fuel cell exhaust can still be used to burn and expand to output propulsion power. In this paper, the turbine-less jet engines integrated with a SOFC and steam injection are proposed to achieve high-speed flight. In order to analyze the performance of the engine, the thermodynamic model is built. Effects of thermodynamic parameters such as water-air ratio are studied. The main results are as follows: the performance of the turbine-less engine is significantly improved by integrating with steam injection. The augment of specific impulse and specific thrust of the engine is 13.13% and 51% respectively compared with the pre-cooling turbojet engine at the water-air ratio of 0.013. The specific impulse of the engine is 1.15 times that of the pre-cooling turbojet engine at Mach 4. Meanwhile, the specific thrust is increased by 26%.