Effect of pumping gas on temperature field and pressure in hollow tungsten arc

Abstract

A hollow tungsten negative pressure arc (HTNA) is a heat source that controls the gas flow inside a tungsten electrode and optimizes the arc output. However, to ensure the widespread applicability of HTNAs, the factors affecting the temperature and pressure distribution of an HTNA should be studied. In this study, the effect of pumping gas on the temperature and pressure distribution of an HTNA is elucidated through experiments and numerical simulations. A double spectral line acquisition system with nine optical transmission fibers was used to obtain the arc light intensity for the temperature calculation and spatial reconstruction. Consequently, a unified numerical model was developed to quantitatively study the physical field distribution under the effect of pumping gas. It was observed that the maximum temperature of the traditional gas tungsten arc (GTA) and hollow tungsten arc (HTA) decreased more than that of the HTNA owing to the effects of pumping gas. By analyzing the current density and flow field, it was concluded that convective heat transfer owing to pumping gas is the primary cause of the temperature difference between the arcs rather than Joule heat. Compared with the effect of the Lorenz force, the arc flow had a more significant effect on the pressure difference between the inner and outer tungsten electrodes. The gas in the arc region flowing into tungsten also affected the arc pressure on the base metal surface. The results of this study are expected to provide guidance for controlling the energy output of the welding arcs.