微波等离子推力器谐振腔的数值模拟与小推力测量实验研究

【作者】 唐金兰；

【导师】 何洪庆；

【作者基本信息】 西北工业大学 ， 航空宇航推进理论与工程， 2002， 博士

【摘要】 微波等离子推力器（Microwave Plasma Thruster—MPT）是一种新型的在研电热推进装置。在航天飞行器上有广阔的应用前景。本论文对MPT微波等离子体耦合流场进行了机理分析和数值模拟，建立了MPT的小推力测量系统，协同进行了MPT真空环境实验研究。主要工作如下： 1．分析了MPT谐振腔内微波能量的转换过程，揭示了其内等离子体的形成是由MPT启动初期的强电场电离形成放电区过渡到稳定工作期的热电离形成稳态等离子体区这一物理本质；研究了影响MPT稳定工作的主要因素，指出微波有效功率与谐振腔内气体压强的匹配是维持等离子体稳定、避免等离子体消失、放电区熄灭的关键因素。 2．采用时域有限差分（FDTD）法数值求解Maxwell方程，分析了MPT无加载谐振腔内的电磁场特性。对TM₀₁₁模，分析了隔板对谐振腔内电磁场分布及谐振频率的影响；对TEM模，分析了内导体形状、位置对谐振腔内电磁场分布的影响；以及它们对启动和稳定工作的影响。 3．采用FDTD法求解Maxwell方程、有限体积法求解N-S方程、单温度局域热平衡模型求解等离子体参数，首次用全数值方法对MPT谐振腔进行了微波等离子体耦合流场的数值模拟，分别分析了TM₀₁₁和TEM两种模式各自的参数匹配关系及其对微波等离子体流场的影响；应用于小型化MPT时，指出了小型化设计参数的合理选取，即：小型化后的MPT，喉径小、工质流量小，消耗的微波功率也小。 4．采用无护套的金属软波导管作为微波传输系统的弹性连件、天平式电磁反馈自动补偿的小推力测量装置，成功地实现了MPT自重与其产生的推力分离、解决了微波传输电缆对MPT小推力测量干扰的关键问题，在实现MPT小推力测量的实际应用中提高了测量精度和稳定性。 5．在国内首次进行了MPT真空环境启动、稳定工作特性和性能实验，测取了MPT的性能参数曲线，研究了微波功率、工质气体流量等参数对MPT性能的影响。更多还原

【Abstract】 Microwave Plasma Thruster (MPT) is a new studying type electro-thermal propulsive device. It has prospective application in spacecraft. In this thesis, the mechanism analysis and numerical simulation on the coupling flow field of microwave plasma within resonant cavity of MPT was discussed and the subsystem of small thrust measurement as well as the vacuum experimental study of MPT were completed. The main works as follows:1. The conversion process of microwave energy within resonant cavity of MPT was analyzed. The physical characteristic of forming plasma within resonant cavity was revealed, i.e. the forming mechanism is a switching process from the ionization caused by strong electric field at the initial stage of MPT’s start to another ionization caused by Joule’s heat at the stage of MPT’s steady work. The main influencing factors of MPT’s steady work were studied. Anther pointed out the matching between pressure in resonant cavity and microwave power is the determinant factor to the plasma whether stabilization or extinguishing.2. With the Finite-Difference Time-Domain (FDTD) method, the characteristic of electromagnetic field within the vacant resonant cavity was analyzed. For TMon model in cylindrical resonant cavity, the influence of the position, material and thickness of the clapboard on electromagnetic field and resonant frequency was studied. For TEM model in coaxial resonant cavity, the influence of shape and position of inner conductor on electromagnetic field, start-up and steady work was studied.3. With the FDTD method to solve the Maxwell equations, with the finite-volume method to solve the N-S equations and with the single temperature local thermal equilibrium to solve plasma, first time to adopt the method of all numerical simulation, the coupling flow field of microwave plasma within resonant cavity of MPT was analyzed. For TM011 model and TEM model, the matching relation between various parameters and its influence on the coupling flow field of microwave plasma within resonant cavity of MPT was studied separately. The reasonable selection of miniaturization design parameters was pointed out in the numerical simulation to be used in MPT miniaturization, i.e. throat, gas flux and microwave power should be smaller suitable after miniaturization.4. Two key problems were solved: 1) to cancel the disturb of microwave cable rigidity on small thrust measurement of MPT adopting soft wave-guide without jacket as elastic linker, 2) to successfully realized separation of self-weight and thrust of MPT adopting small thrust measurement device of balance type, electromagnetic feedback and automatically compensation. So, the measurement precisionand stability were greatly raised in actually application of small thrust measurement device.5. Experimental study on start-up, steady work and performance of MPT were completed first time in China. The performance curves of MPT were obtained and the influence of parameters such as microwave power, gas flux, etc. on performance was studied.更多还原