Study On Thermal Cycle Of Air-breathing Precooling Engine And Heat Transfer Characteristics Of Precooler

Synergistic Air-Breathing Rocket Engine(SABRE)is a very valuable combined air-breathing and pre-cooling engine.Its system structure is complex and the coupling between components is strong.Air precooler is the core component of SABRE engine.Its function is to achieve high efficiency heat transfer between air and cryogenic helium in a short time.How to achieve high temperature difference,high efficiency,compact and light weight is the core design technology of precooled aspiration engine.Aiming at the thermal cycle system of SABRE engine,this paper models the thermal cycle of SABRE engine,and studies the main factors affecting the performance of the power system of SABRE engine and their influencing rules.It has important theoretical and practical significance for the thermal cycle system of SABRE engine.In this paper,the flow and heat transfer characteristics of supercritical helium in a single straight tube and the flow distribution and flow resistance characteristics of the pipe connecting components are studied by numerical simulation.For the SABRE engine pre-cooler,the effects of the number of tube rows,tube spacing,air velocity,temperature and other factors on the flow and heat transfer characteristics of the pre-cooler are studied by numerical simulation.It is found that the unit thrust and specific impulse of SABRE-3 engine increase by about 1% for every 10 K rise in air temperature after precooling;the unit thrust of SABRE-3 engine decreases by about 15% and specific impulse decreases by 45% when helium flow increases from 75kg/s to 115kg/s;and the total pressure recovery factor of air side of SABRE-4 precooler decreases engine thrust and specific impulse slightly,but reduces the output of air compressor.Increasing the helium flow rate slightly reduces the engine efficiency and unit thrust,but greatly reduces the consumption of hydrogen and increases the specific impulse of the engine.Increasing the tube spacing of the pre-cooler will increase the average heat transfer coefficient of the air side of the pre-cooler and reduce the total pressure loss of the air,but will reduce the precooling effect of the air.Increasing the number of tube rows will reduce the average heat transfer coefficient on the air side,but it can reduce the air temperature after pre-cooling and enhance the pre-cooling effect.Increasing the helium/air heat capacity ratio can increase the average heat transfer coefficients of the air side and helium side at the same time,and reduce the air outlet temperature.The incident angle of air has little effect on the heat transfer of air side and helium side,but has a great influence on the total pressure recovery coefficient of air side.