【摘要】 为了延长在低地轨道(LEO)和极低地球轨道(VLEO)的卫星寿命,使用吸气式电推进器提供推力成为研究的热点。然而,150 km高度以上的大气非常稀薄,需要将气体收集压缩之后才能供给推进器使用,所以对气体收集装置的结构设计非常重要。本文使用直接仿真蒙特卡洛(DSMC)方法对进气装置进行数值模拟,得到进气装置内外流场的平均数密度和速度分布云图,发现进气装置前段流场存在类激波结构,流场存在热力学非平衡现象;研究了压缩角度θ(7°～45°)和进出口直径比a(3～7)对流动的影响,最后分析了分子与壁面碰撞模型对收集效果的影响。结果表明,在出口直径相等的情况下,压缩段角度越大,出口截面平均气体速度越大;当压缩角度θ为15°和30°时,出口粒子流量较大;入口直径增大时,粒子浓度上升速度减慢;粒子流量和粒子浓度比在进出口直径比a为6时均存在最大值,当直径进一步增大时,出口处粒子浓度反而降低;气体分子在完全漫反射模型下收集效率更高。更多还原

【Abstract】 In order to extend the lifetime of satellites in low earth orbit(LEO) and very low earth orbit(VLEO), application of atmosphere-breathing electric propulsion(ABEP) system has become a research focus in recent years. However, the atmosphere above 150 km is very thin, where the gas needs to be collected and compressed before being supplied to thrusters, so the structural design of gas collection device is crucial. In this research, Direct Simulation Monte Carlo(DSMC) method is used to conduct numerical simulation of air intake device. The average density and velocity distribution of inner and exterior flow fields of the air intake device are obtained in this way, and a shock-like structure and the thermodynamic non-equilibrium phenomenon are found in the flow field at the front section of the intake device.Besides, the effects of the compression angle θ(7°～45°) and the diameter ratio of inlet and outlet α(3～7) on the flow are studied, and the influence of molecular-wall collision model on collection effect is analyzed. The results show that with equal outlet diameter, the larger the compression section angle, the greater the average gas velocity at outlet section; when θ is 15° or 30°, the outflow of particles is larger. With the increase of inlet diameter, the rising rate of particle concentration slows down; when the value of α is 6, the particle flow rate and particle concentration ratio both reach their maximum values, while the particle concentration at outlet decreases as the diameter further increases. In addition, the collection efficiency of gas molecules is higher under completely diffuse reflection model.更多还原