Numerical Simulation of the Effect of Annular Boss Structure on DC Arc Anode Attachment

In recent experiments, it is found that an annular boss anode structure can be used to adjust the arc anode attachment mode, which is expected to be beneficial for improving the anode heat transfer. To understand the effect of annular boss structure on the arc anode attachment, two-dimensional axisymmetric numerical simulation is performed based on a two-temperature chemical non-equilibrium model. The results show that the existence of the annular boss changes the distribution of electric field along the anode surface, and then the arc is attracted to the annular boss because of the enhancement of the nearby electric field intensity. This results in a decrease in the peak current density and a change in its radial distribution in the anode arc attachment region. As a result, the magnitude and direction of the Lorentz force are also changed, acting to suppress the formation of the anode jet. Compared with the case of planar anode, the heat flux of anode with annular boss decreases significantly due to the diffusive arc attachment, which results in significant reduction of the maximum anode temperature. Besides, the effect of the size of annular boss on arc anode attachment behavior has been investigated and the numerical results show that a reasonable choice of inner diameter is important for the formation of diffusion-type anode arc attachment.