脉冲等离子体推力器宏观特性数值研究

Numerical analysis on macro-characteristics of pulsed plasma thruster

关键词:  脉冲等离子体推力器  宏观特性  延时气化  数值仿真

Key words:  Pulsed plasma thruster  Macro-characteristics  Late time ablation  Numerical simulation

摘要:

为了揭示脉冲等离子体推力器(Pulsed plasma thruster,PPT)的宏观工作特性,以传统“弹丸”模型为基础,提出了一种基于电磁和气动耦合加速机理的计算模型以及延时气化效应的评估方法,并与LES-6,LES-8/9 PPT进行模型验证和实验对比。结果表明,计算所获得的PPT脉冲烧蚀质量等宏观特性与实验数据吻合较好；脉冲烧蚀质量中仅有较少一部分(LES-6约10%,LES-8/9约28%)被离子化和电磁加速排出(约31.6km/s),其余绝大部分则是在主放电结束后以中性气体混和物低速排出(约460~680m/s)；电磁加速对PPT元冲量的贡献是主要的(LES-6约77%,LES-8/9约86%)；增强电磁加速,尤其是减少延时气化效应对PPT效率的提高是十分必要的。

Abstract:

In order to study the macro-characteristics of pulsed plasma thruster (PPT) operation process, a computational model for electromagnetic,aerodynamic coupling acceleration mechanism and analytic method for the late time ablation (LTA) were formed on the basis of traditional slug model. Numerical simulation was carried out on the foundation of LES-6, LES-8/9 experimental PPT. Simulation results show a good agreement with experimental data.It indicates that only a small fraction(LES-6 about 10%,LES-8/9 about 28%)of the total ablated mass is produced during the current pulse and has the opportunity to be ionized and magnetically accelerated to high exhaust speeds(About 31.6km/s).The rest gradually evaporates during much later times as a neutral gas that expands at relatively low speed(About 460~680m/s).Electromagnetic acceleration is the most important source of thruster impulse(LES-6 about 77%,LES-8/9 about 86%).Enhancing of electromagnetic contribution and reduction of LTA effect would significantly improve the efficiency of the thruster.