Air Turbo Ramjet Expander Performance Analysis Based on Gases Dissociation Effect

摘要

An Air Turbo-Ramjet Expander(ATREX) is one of the most preferable propulsion system for high speed vehicles. The ATREX off-design performance with components characteristics is first assessed and analyzed though a mathematical model, and the engine operating line on the flight path with maximum specific impulse and maximum thrust are obtained. An ATREX precooler off-design model is presented based on fully counter-flow type ε-NTU relation, and the working fluid dissociation effect is taken into consideration through chemical equilibrium method. The engine thrust and specific impulse are found to be overestimated without considering the gases dissociation especially at high flight Mach number conditions. The engine overall performance on allowed maximum rotation speed line is obtained though adjusting the fuel mass flow rate, pump pressure ratio and the nozzle throat area, and the engine components matching laws between control factors and controlled engine parameters are proposed and explained through reduction to absurdity method. The results show, at low flight Mach number conditions, when the compressor operating point moves from surge line to choking, the decreasing of compressor efficiency slows down the increasing trend of air-fuel ratio, and the engine specific impulse starts to decrease with the air-fuel ratio. But at high flight Mach number condition, because of the high total temperature free stream, the compressor operating at low corrected rotation speed area with low pressure ratio. The effect of compressor efficiency drop becomes weak, and the specific impulse increases with the air-fuel ratio along the allowed maximum rotation speed line. Finally, the engine operating line with optimum thrust and optimum specific impulse along the trajectory are achieved.