Performance analysis of precooled turbojet engine with a low-temperature endothermic fuel

For hydrocarbon-fueled TBCC engines, precooling is a crucial technology to solve “thrust gap” by expanding the flight Mach number of the turbojet engine, which can bring a sharp reduction of the specific impulse due to insufficient heat sink of hydrocarbon fuel. A low-temperature endothermic fuel precooling scheme is a great potential way to solve this problem. Heat sink experiments and thermodynamic cycle analysis are used to verify the effectiveness of the low-temperature endothermic fuel precooling scheme in improving specific impulse performance. The experiment results indicated that low-temperature endothermic fuel has a more considerable heat sink at lower temperatures than traditional endothermic hydrocarbon fuel. The results of thermodynamic cycle analysis show that the low-temperature endothermic fuel precooling scheme can effectively improve the specific impulse. Maximum specific impulse can reach above 800s with the low-temperature endothermic fuel precooling scheme, which is below 400s with hydrocarbon fuel precooling at Ma₀ = 3.0. When cracking rate equals 1.0, and precooling efficiency equals 0.85, maximum specific impulse can reach 600s, increased by approximately 1.4 times at Ma₀ = 4.0. The feasibility of precooled turbojet with the low-temperature endothermic fuel precooling scheme was preliminarily verified through this work.