Anode attachment stability and anode heat transfer for high-intensity arcs with lateral gas flow

Abstract

This study determined the motion of an anode attachment and the heat flux to the anode for a configuration in which the arc axis is perpendicular to the anode surface with the plasma gas flowing along the arc axis, and with lateral injection of different gases parallel to the anode surface. The arc is stabilized by a constrictor except for a gap of 10 mm, the arc currents are 75 and 100 A, the plasma gas flow rate is 5 slm of argon, and the lateral gas flow rate is 0 to 25 slm, with argon, nitrogen, or helium gas that is injected laterally. High-speed videography and calorimetric measurements of the anode cooling water temperature increase are used to characterize the anode attachment. Results show that different modes of anode attachment exist, including a steady deflected anode root, a randomly fluctuating attachment, and a periodically fluctuating attachment. When the anode spot appears, the lateral gas produces an arc voltage increase. The total anode heat transfer changes with different lateral gas flow rates and for different attachments modes. This effect probably occurs because lateral gas flow causes a convective heat loss from the arc to the chamber walls.