针对上层大气层吸气式电推进系统进气道的宽范围设计难题,采用直接模拟Monte Carlo(Direct Simulation Monte Carlo,DSMC)方法对进气道内部流动问题进行了系统的数值模拟,探索气体压力和质量通量的分布特征,考虑飞行高度的影响规律和作用机理,评估自由分子流假设的有效性.结果表明,随着飞行高度的升高,进气道内部的无量纲压力逐渐降低,表明进气道的压缩性能减弱.因此,当吸气式电推进系统运行在上层大气层的较高区域时,应特别留意进气道的压缩性能.此外,随着飞行高度的升高,气体分子之间碰撞的减弱导致无量纲质量通量在压缩段中心区域减小,在电离加速段中部增大.对于120km左右的高度,进气道流动中气体分子之间的碰撞仍然具有举足轻重的作用,自由分子流假设给出的气体压力和质量通量与标准DSMC结果存在明显的差异.对于180km及以上的高度,进气道流动可以认为是自由分子流,即气体分子之间的碰撞可以忽略,自由分子流假设给出的气体压力和质量通量与标准DSMC结果一致,此时采用自由分子流假设是合理的.
Numerical analysis of inlet flows in an atmosphere-breathing electric propulsion system
A comprehensive numerical study was conducted using the direct simulation Monte Carlo(DSMC)method for investigating the gas flows inside the inlet of an atmosphere-breathing electric propulsion(ABEP)system.This was done to obtain various inlet designs for the ABEP system operating in the upper atmosphere ranging from 120 to 300 km.The primary objective was to gain insights into the gas-pressure and mass-flux distributions,analyze the effect of operation altitudes on inlet performances,and assess the rationality of the free molecular flow(FMF)assumption.The results showed that gas pressure decreased with increasing altitude,indicating a weaker compression performance of the inlet at higher altitudes.Thus,future research must comprehensively analyze the compression performance of the inlet when the ABEP system operates at higher altitudes.Further,the dimensionless mass flux decreased in the central region of the compression section at higher altitudes but increased in the center of the ionization section;this finding can be attributed to the weakened collisions between gas molecules.At an altitude of～120 km,collisions between gas molecules played an important role:there was a large discrepancy in the gas-pressure and mass-flux determination results based on the FMF assumption and standard DSMC method.However,for altitudes＞180 km,gas flows in the inlet were characterized by free molecular flows.The results based on the FMF assumption were consistent with those of the standard DSMC method,indicating the rationality of the FMF assumption at these altitudes.
万方数据
维普
