同轴微阴极电弧推力器的粒子网格法数值模拟

Particle-in-cell simulation of a co-axial micro-cathode arc thruster

采用粒子网格(Particle-In-Cell,PIC)方法对同轴微阴极电弧推力器(μCAT)工作过程进行了模拟研究,并应用自相似方法对模型进行简化,获得了推力器羽流区的电子数密度分布、离子数密度分布、电势分布及离子轴向平均速度,通过改变磁感应强度和位形分析磁场对推力器内等离子体运动特性及推力器性能的影响。计算结果表明,电子被外加磁场捕获约束在磁力线附近,低速离子与高速电子形成的双极扩散电场加速离子喷出;在相同流量情况下,磁感应强度0.02T时,离子返流严重,磁感应强度0.05~0.30T时,磁感应强度变化对速度影响较小;磁场位形对离子运动和推力器性能有较大影响,磁力线与轴线夹角较小时离子速度下降明显,夹角较大时离子返流严重。

A modeling study was performed to investigate the working process of a co-axial micro-cathode arc thruster with particle-in-cell（PIC）method,and the self-similar method was applied to simplify the simulation model.The distribution of electron number density,ion number density,electric potential and axial average ion velocity in the thruster plume region was obtained.The influences of magnetic field on plasma motion characteristics and thrusterperformance were studied by changing magnetic flux density and magnetic field topology.The results show that electrons are constrained by the applied magnetic field,cycling around magnetic field lines,and that ions are accelerated by the ambipolar diffusion electric field produced by slower ions and faster electrons.With the same mass flow rate,the ion reflux is severe when the magnetic flux density is 0.02 T,while the ion velocity is less affected by the magnetic flux density when the magnetic flux density is 0.05~0.30 T.Magnetic field topology has great influence on the ion motion and thruster performance.The ion velocity decreases obviously when the angle between the axis and magnetic field lines is small,while the ion reflux is severe when the angle is large.