磁屏蔽对小功率霍尔推力器性能的影响机理

Impact Mechanisms of Magnetic Shielding on Performance of Low-Power Hall Thrusters

关键词:  小功率霍尔推力器  磁屏蔽  性能衰减  数值模拟  光功耗

Key words:  Low-power Hall thrusters  Magnetic shielding  Performance attenuation  Numerical calculation  Light power consumption

摘要:

霍尔磁屏蔽技术是一种延长推力器工作寿命的技术，但对于小功率霍尔推力器而言，磁屏蔽作用会对推进性能产生较大的衰减影响。为深入研究这种影响机制，本文建立一种结合单元粒子法（PIC）/等离子体化学动力学碰撞（PCD）的模型来求解霍尔推力器等离子体流场。为验证数值模型的正确性，在真空舱内开展验证试验，针对无磁屏蔽工况和高强磁屏蔽工况分别进行推力、特征光谱的测量，以同等工况下的计算值和试验测量值进行对比，验证模型的精度。在此基础上，利用数值模型针对四种工况下的推力器光功耗数据进行计算，并分析相关规律的物理机制。结果表明，光功耗是影响推力器性能下降的主要因素，最强磁屏蔽工况中的光功耗能效可超过24%（无屏蔽工况：13.6%），该特性与电子温度分布整体外推、电子升温有直接关系，而本质原因在于放电室出口位置的磁镜磁场构型。

Abstract:

The magnetic shielding technology in Hall thrusters is a kind of strategy to increase the lifetime. However， the magnetic shielding effect has exerted a negative influence on the propulsion performance of low-power hall thrusters. In order to further study this side effect， a numerical model based on the particle in cell （PIC） and plasma chemical dynamics （PCD） has been established to solve the plasma flow field in Hall thruster. A rectification test was conducted in the vacuum chamber to validate the correctness of this model. The parameters of thrust and spectral power in both unshielded thruster and magnetically shielded thruster have been measured respectively， and the comparison of the calculation and the test results was obtained to examine the accuracy of the model. Based on those above， the light power consumption in different four cases of Hall thrusters was solved numerically. Moreover， the relevant physical mechanisms were discussed. The main conclusions show that， the light power consumption is the main factor to impair the thruster performance， and the consumption efficiency in the strongest magnetically shielded case is more than 24% approximately （unshielded case： 13.6%）. The characteristic of this physical process is directly associated with the extension of the whole electron temperature distribution and the increase of the electron temperature， which essentially originated from the magnetic mirror effect at the discharge chamber exit.