高功率磁屏蔽霍尔推力器的降阶粒子模拟
Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster
AI总结：
本文采用新型降阶PIC格式对20 kW磁屏蔽霍尔推力器进行轴向-方位角和径向-方位角模拟，在无特设电子迁移率模型下自洽解析650 μs放电演化，并以70%至80%精度逼近实验性能，同时揭示了出口附近长波长低频波模对电子输运的显著影响。
摘要：
高功率磁屏蔽霍尔推力器近年来应运而生，以满足下一代空间任务的需求。尽管少数此类推力器目前正处于后期研制阶段，但在这些具有非常规磁场拓扑结构的大型推力器中，关于等离子体的行为与演化仍存在许多未解之谜。鉴于霍尔推力器中等离子体过程具有复杂的多维特性，高保真粒子模拟（particle-in-cell，PIC）是研究复杂等离子体行为的最佳工具。然而，传统PIC格式的巨大计算成本使得在不采用任何改变物理的加速因子的情况下模拟高功率推力器变得不可行。因此，在本文中，我们通过沿轴向-方位角和径向-方位角坐标对一台20 kW磁屏蔽霍尔推力器进行模拟，展示了新型降阶PIC格式在高功率霍尔推力器低成本、自洽研究中的适用性。轴向-方位角模拟在推力器固有三维构型的相当简化的表示下，针对三种工况进行。尽管如此，我们在没有任何特设电子迁移率模型的情况下，自洽地解析了前所未有的650 μs放电演化过程，捕捉到多个呼吸周期，并在各工况下以70%至80%的精度逼近实验性能参数。径向-方位角模拟进一步揭示了方位角不稳定性的演化以及由此引起的电子跨场迁移率和等离子体-壁面相互作用的变化。特别是，我们观察到在推力器通道出口平面附近发展出一种长波长、相对低频的波模，该波模诱导了显著的电子输运。
英文摘要：
High-power magnetically shielded Hall thrusters have recently emerged to meet the needs of the next-generation space missions. Even though a few such thrusters are currently undergoing their late-stage development campaigns, many unanswered questions yet exist concerning the behavior and evolution of the plasma in these large-size thrusters that feature an unconventional magnetic field topology. Noting the complex, multi-dimensional nature of plasma processes in Hall thrusters, high-fidelity particle-in-cell simulations are optimal tools to study the intricate plasma behavior. Nonetheless, the significant computational cost of traditional PIC schemes renders simulating high-power thrusters without any physics-altering speed-up factors unfeasible. Thus, in this article, we demonstrate the applicability of the novel reduced-order PIC scheme for a cost-efficient, self-consistent study of the high-power Hall thrusters by performing simulations of a 20 kW magnetically shielded Hall thruster along the axial-azimuthal and radial-azimuthal coordinates. The axial-azimuthal simulations are performed for three operating conditions in a rather simplified representation of the thruster's inherently 3D configuration. Nevertheless, we resolved self-consistently an unprecedented 650 us of the discharge evolution without any ad-hoc electron mobility model, capturing several breathing cycles and approximating the experimental performance parameters with an accuracy of 70 to 80 % across the operating conditions. The radial-azimuthal simulations casted further light on the evolution of the azimuthal instabilities and the resulting variations in the electrons' cross-field mobility and the plasma-wall interactions. Particularly, we observed the development of a long-wavelength, relatively low-frequency wave mode near the exit plane of the thruster's channel that induces a notable electron transport.
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