Numerical Simulation Of The Microwave Plasma Thruster Cavity With Small Thrust Measurement Tests

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.