Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

Abstract

A transferred arc system consisting of a crucible type anode and hollow cathode with gas injection is being considered for melting and evaporation of materials to improve the heat transfer efficiency. Knowledge of arc behavior inside the crucible and the effect of gas injection through the cathode on the characteristics of the arc are required to optimize the process parameters for better process efficiency. The available literature on this is very limited. A 2D steady-state axi-symmetrical mathematical model of a DC transferred arc is developed and the plasma arc created between a hollow cathode with gas injection and a crucible anode is simulated. The effects of cathode geometry and gas flow through the cathode on the arc characteristics are studied for different electrode gaps and arc currents. The effect of gas flow through the cathode on the arc voltage is clarified for various electrode gaps and arc currents. The gas flow through the cathode is strong enough to push the arc root attachment from the center of the anode and the plasma covers the entire surface of the crucible bottom at higher gas flow rates. Irrespective of the gas flow rate, arc current, and arc length, the higher arc heating efficiency is achieved when the arc root attachment starts to move away from the center of the anode/arc voltage is minimal. The characteristics of the arc inside the crucible and open arc are compared for different flow rates of the gas injected through the cathode. The present model is validated by comparing the predicted results with previously published results.

Chromium, a promising cathode candidate for homogeneous arc erosion in air

“…Cathode erosion has been considered an inevitable process in arc plasma applications, such as welding, plasma cutting [1,2], arc heaters [3][4][5], and vacuum interrupters [6][7][8][9]. The constant testing demands of arc heaters for maximum operating power and full-power operating time render the cathode erosion an urgent technical problem [10].…”