基于MHD的小间隙真空电弧仿真研究

Magnet Hydro-Dynamic Simulation of Vacuum Arc at Small Gap Length

真空开关电弧电流过零前的电弧等离子体状态对真空开关能否顺利开断具有十分重要的影响。本文在建立小间隙真空电弧磁流体动力学(MHD)模型的基础上,采用通用计算流体力学仿真软件对电弧电流过零前0.5 ms时的电弧等离子体的特性进行数值仿真研究。计算得到了真空电弧等离子体压力、等离子体密度、离子纵向速度、阳极表面纵向电流密度和电弧电压等的空间分布。仿真结果表明:从阴极到阳极,真空电弧等离子体压力和密度逐渐增大,而等离子体速度逐渐减小;阳极表面电流密度存在较大径向梯度,最大值低于形成阳极斑点的极限收缩电流,阳极仍不活跃。仿真得到的等离子体密度分布与高速摄像机拍摄得到的CMOS图像光强基本吻合,计算得到的电弧电压与测得的电弧电压是一致的,从而验证了本模型的可行性。

The plasma of the vacuum arc at small gap length,0.5 ms before the arc current passes zero,was modeled and simulated,based on the magnet hydro dynamic（MHD） theory,with a software package of the computational fluid dynamics.The calculations include the plasma density,its pressure distributions,axial velocity of ions,axial current density on anode surfaces,and spatial distribution of arc potential.The simulated results show that as the position moves away from the cathode to the anode,the pressure and density of the plasma gradually increase;whereas its axial velocity decreases.A fairly large radial gradient of the current density exists on the anode surface,and its peak current density is lower than the threshold current density of the anode-spot formation.So the anode remains passive.The simulated results agree rather well with the CMOS images taken with a high speed camera.