霍尔推力器通道宽度对电离特性的影响

Influences of discharge channel width on ionization characteristics in Hall thrusters

关键词:  霍尔推力器  通道宽度  电离特性  粒子模拟  光谱诊断

Key words:  Hall effect thruster  Channel width  Ionization characteristic  Particle-in-cell  Spectrum diagnosis

摘要:

为了研究霍尔推力器通道宽度对电离特性的影响,采用以数值模拟为主、实验验证为辅两种手段相结合的方式。所建立的数学模型是基于蒙特卡洛方法的二维完全动力学粒子模型,实验选择了与等离子体无接触的光谱诊断方法。计算和实验两方面的结果都发现随着宽度的增加,电子电离工质气体的速率增加,电离更加有效,而且电离区域变得集中的规律。通过进一步的计算发现,电离特性的明显差异和电子与壁面碰撞频率随宽度增加而减小,电子温度随之升高有着密切关系。电子温度升高一方面会对电离特性起到促进作用,另一方面也会使电离消耗的能量增加。由于稳态时的电子温度是由电子能量平衡机制决定的,因此对电子能量平衡方程进行深入分析之后发现,在研究通道宽度影响电离特性这一物理问题上,电子在壁面上的能量损失是决定电子温度的主导因素,而电离损失仅属于次要因素,宽度增加有利于改善推力器的电离特性。

Abstract:

The ionization characteristics in Hall thrusters with different discharge channel width were investigated by both numerical and experimental methods. Two-dimensional particle-in-cell method based on Monte Carlo collision was utilized for simulation, while no-contact spectrum diagnosis was introduced in the experiment. Both of the calculated and measured results show that with the increasing of channel width, the ionization rate of propulsion increased, the ionization becomes more effective and the ionization area tenas to be more concentrated. Further calculation results indicate that the striking difference of ionization characteristic is closely related to the phenomenon that with the increase of channel width. The collision frequency is reduces between the electron and wall while the electron temperature raises. However, the rising electron temperature not only promotes the neutral ionized but also increases the loss of electron energy. Since the electron temperature in steady state was determined by the electron energy balance mechanism, through analyzing electron energy balance equation, we have found the wall loss is dominant factor affecting the electron temperature when the channel width changes, while the ionization loss was just a subordination factor. The increase of channel width is in favor of improving ionization characteristics. 