Modeling of macro-particles in vacuum arc jet before current zero with axial magnetic field

Abstract

In this paper, macroparticle (MP) characteristics in vacuum arc jet (VAJ) before current zero under the influence of the axial magnetic field (AMF) are investigated by numerical simulation. The magnetohydrodynamic model is used to describe the VAJ, while MPs are treated as the discrete phase. The model for MPs is established considering the charging process, motion process, heat transfer process, and rotation process. Simulation results show that smaller MPs are more likely to reach higher velocity and rotate faster. But the MP cannot rotate once due to the short flight distance. Both a higher VAJ current and a smaller VAJ angle can lead to a stronger heating process, evaporation process, and acceleration process of the MP because of higher plasma density and temperature. Although AMF can affect plasma parameters obviously, it can hardly change the MP motion direction. Since plasma density is rarefied far from the cathode center, most MP parameters tend to become steady after some flight distance. Some small MPs can reach the anode with high velocity instead of being evaporated completely. The collision between these MPs and the electrode may be harmful to the postarc period.