Cathode erosion evolution and instability analysis of liquid-metal jets in high-pressure arcs

Abstract

The metallic droplets generated by high-voltage gas arc erosion on electrode surfaces are the key factors constraining the reliability and service life of gas-insulated switches. The process of cathode erosion evolution forming liquid metal jets is the critical link in understanding the generation of metal droplets. This study establishes a two-dimensional numerical model of spot erosion on the cathode under high-pressure arc conditions, aiming to investigate the evolution of spots under arc plasma interactions and analyze the generation mechanisms of metallic particles during electrode erosion in conjunction with the instability analysis of liquid metal flow. The model divides the near-cathode region structure into sheath and presheath layers. By comprehensively considering the effects of multiple particle flows, the current density distribution of spots can be obtained through coupled solutions by establishing an electron energy balance equation in the presheath layer. The simulation results indicate that under the pressure gradient, liquid metal moves from the spot center toward the crater edges, forming wrinkles on the crater walls. A small amount of liquid metal splatters away from the electrode surface. The instability analysis of liquid metal flow reveals that the process of jet formation and droplet breakup in the erosion crater of spots is predominantly associated with Rayleigh–Plateau instability, with corresponding analysis conducted on the time required for this instability to develop.