外形设计对微喷管性能的影响

利用直接模拟蒙特卡罗法对钟形、喇叭形和锥形等三种不同形状微喷管进行管内气体流动模拟,并对不同温度及入口压力下各形状喷管的性能变化进行模拟分析,模拟中采用与实际分子碰撞过程更为接近的内能松弛模型及CLL物面反射模型。研究结果表明钟形微喷管因扩张段回流区的存在,其推力性能明显低于喇叭形和锥形微喷管,锥形微喷管的推力性能同喇叭形微喷管较为相近。三种形状的微喷管推力值都随着入口温度的升高而降低,而微喷管的推力效率随着入口温度的升高而上升,入口压力的变化对微喷管推力有较大影响,但对微喷管的推力效率影响并不显著。

Effects of geometry design on micro nozzle's performance

The Direct Simulation Monte-Carlo method is applied to simulate the flow in micronozzles with conical,bell,and trumpet shaped diverging sections,and the variations of each nozzle's performance under different inlet temperature and pressure.The internal energy relaxation model and Cercignani-Lampis-Lord(CLL) molecule surface reflection model are applied in the simulation,which are extraordinary similar to real molecule collision process.The study indicates that the thrust performance of bell nozzle is apparently lower than that of trumpet and conical nozzle because of the influence of circumfluence region in the diverging section,while the difference of thrust performance between conical nozzle and trumpet nozzle is insignificant.The thrust produced by the three nozzles declines as the temperature of inlet flow increases,however,the thrust coefficient of nozzles increases accordingly.In general,the inlet pressure variations have considerable influence on the thrust of the nozzle.While the influence of inlet pressure variations on the thrust coefficient of the nozzle is insignificant.