离子发动机加速栅极孔扩大腐蚀的粒子模拟

Particle Simulation of the Acceleration Grid Aperture Erosion in Ion Thruster

为研究离子发动机加速栅极孔扩大腐蚀速的特征及影响规律,采用单元内粒子——蒙特卡罗碰撞(PIC-MCC)方法,结合溅射腐蚀模型,模拟了栅极间束流离子及交换电荷(CEX)离子的分布情况,得到离子发动机加速栅极孔扩大腐蚀情况及平均腐蚀率,为0.0176μm/h。进一步研究了工作参数和几何参数对其影响,并建立了适用于工程应用的加速栅极孔扩大腐蚀预测模型。结果表明,在影响孔扩大腐蚀率各种因素中,束流电流密度和中性气体密度的影响最大。因此,在离子发动机直径一定的情况下,提高放电室出口等离子体密度的均匀性及推进剂利用率,是提高栅极寿命的根本途径。

In order to investigate the characteristic and impact factors of the aperture enlargement ero- sion of the ion thruster accelerator grid, the Particle in Cell-Mont Carlo（PIC-MCC） method combined with the sputtering erosion model was used to simulate the distribution of the beamlet ions and charge exchange （CEX） ions. Then the aperture enlargement erosion rate of the NSTAR ion thruster accelerate grid was cal- culated and the value was 0. 0176μm/h. The effects of thruster operating parameters and grid geometry pa- rameters on the aperture enlargement erosion rate were studied. Combined with the computational results, a model for the prediction of the aperture enlargement erosion rate were established. The results indicate that among all the factors the beamlet current and neutral gas density have the greatest impact on the erosion rate. Thus the essential means to extend the life of the accelerate grid can improve the flatness of the plasma distribution in the discharge chamber exit and the propellant utility.