霍尔推进器预电离对低频振荡及壁面腐蚀影响的机理研究

发布时间：2018-06-25 16:11

本文选题：霍尔推进器 + 低频振荡　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：霍尔推进器(Hall Thruster)是一种利用正交电磁场作用来实现工质原子电离以及粒子加速的装置,由于具有效率和比冲较高,寿命较长的特点,近年来在深空探测和微小卫星姿态控制等领域获得了广泛的应用。但是,在航天器任务向多元化发展的大背景下,人们对于霍尔推进器的工作寿命和工作状态的稳定性要求也越来越高。实验证明,预电离可以对放电腔内的物理过程以及稳态下的物理参数产生影响,但是具体的影响过程以及预电离率的确定还没有人做过系统分析,本文即针对预电离对象对低频振荡以及缓冲腔的壁面腐蚀状况展开研究。首先,本文建立了基于fully-kinetic PIC-MCC(质点网格法-蒙特卡洛碰撞法)算法的二维轴对称模型来对霍尔推进器放电通道内的物理过程进行数值模拟,该程序模型包括三部分:计算模型的建立及参数设置,等离子体模拟程序以及腐蚀计算程序。其中,由于PIC算法计算量巨大,通常采用缩放粒子质量以及增大介电常数的方法来加快计算收敛,本文通过缩小不同倍数的重粒子质量探究了缩放粒子质量这种加速方法对霍尔推进器稳定形态物理参数的影响,并根据模拟结果选择了合适的缩放倍数。其次,低频振荡是霍尔推进器工作状态中观察到的一种放电电流自发震荡的现象。新型霍尔推进器在原有霍尔推进器的基础上增加了缓冲腔,实验证明缓冲腔的增加有效抑制了放电通道的低频振荡。本文的主要模拟工作就基于霍尔推进器放电通道内低频振荡现象的抑制来展开,通过在原子入射时增加不同的离子数来模拟不同预电离的等离子体,然后将不同预电离率下得到的放电电流进行快速傅里叶变换得到震荡频谱,并分析预电离与低频振荡之间的相互关系。此外,本文还模拟了SPT-100型Hall推进器的壁面腐蚀过程,探究了预电离对推进器壁面腐蚀的影响,其中壁面腐蚀的速率是根据壁面材料的溅射产额公式计算得出的。通过给出缓冲区不同的预电离率,分析与之相对应的预电离率作用下器壁腐蚀演化的规律。研究结果表明,随着预电离率的逐渐增大,霍尔推进器放电通道内的低频振荡现象有所减弱,但是放电通道的壁面腐蚀状况却也随之增加。因此,基于预电离能够抑制低频振荡却加剧腐蚀的特性,在进行新一代推进器的研发过程中要合理选择预电离率以提高推进器的综合性能和寿命。
[Abstract]:Hall thruster is a device which uses orthogonal electromagnetic field to realize atomic ionization and particle acceleration of working fluid. Because of its high efficiency, high specific impulse and long life, Hall thruster is a kind of device. In recent years, it has been widely used in deep space exploration and micro satellite attitude control. However, with the development of spacecraft missions, the stability of the working life and working state of Hall thrusters is becoming more and more important. The experimental results show that preionization can affect the physical process in the discharge cavity and the physical parameters in the steady state, but no systematic analysis has been done on the specific influence process and the determination of the preionization rate. In this paper, the low frequency oscillation of preionization object and the wall corrosion of buffer cavity are studied. Firstly, a two-dimensional axisymmetric model based on fully-kinetic PIC-MCC (Particle mesh method-Monte Carlo collision) algorithm is established to simulate the physical process in the discharge channel of Hall thruster. The program model consists of three parts: the establishment of the calculation model and parameter setting, the plasma simulation program and the corrosion calculation program. The PIC algorithm usually uses the methods of scaling the particle mass and increasing the dielectric constant to speed up the convergence of the calculation. In this paper, the effect of scaling particle mass on the physical parameters of stable morphology of Hall thruster is investigated by reducing the mass of heavy particles of different times, and the appropriate scaling times are selected according to the simulation results. Secondly, low frequency oscillation is a kind of spontaneous oscillation of discharge current observed in the working state of Hall thruster. The new type of Hall thruster increases the buffer cavity on the basis of the original Hall thruster. The experiment shows that the increase of the buffer cavity effectively suppresses the low frequency oscillation of the discharge channel. The main simulation work in this paper is based on the suppression of the low frequency oscillation in the Hall propeller discharge channel. Different preionized plasma are simulated by increasing the number of ions when the atom is incident. Then the discharge current obtained under different preionization rates is analyzed by fast Fourier transform and the correlation between preionization and low frequency oscillation is analyzed. In addition, the wall corrosion process of SPT-100 Hall thruster is simulated, and the influence of preionization on the wall corrosion of the propeller is investigated. The rate of wall corrosion is calculated according to the sputtering yield formula of the wall material. By giving different preionization rates of buffer zone, the law of corrosion evolution of the vessel wall under the action of corresponding preionization rate is analyzed. The results show that with the increase of preionization rate, the low frequency oscillation in the Hall propeller discharge channel weakens, but the wall corrosion of the discharge channel increases. Therefore, based on the characteristic that preionization can suppress the low frequency oscillation but aggravate the corrosion, the preionization rate should be reasonably selected in the research and development of the new generation thruster in order to improve the comprehensive performance and life of the thruster.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V439

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