Numerical analysis of free-burning argon arcs based on the local thermodynamic equilibrium model at various electrical currents

• Free-burning argon arcs were investigated at various working currents numerically.
• The relationships between the current, the velocity and the temperature were found.
• Some discrepancies were shown in the results of pressure and electric potential.
• Those should be supplemented by the non-equilibrium situation near electrodes.

Free-burning arcs where the work piece acts as an anode were numerically analyzed using a computational domain including the arc itself and its anode region based on the local thermodynamic equilibrium model. Because the major arc parameters such as temperature, axial velocity, electric potential difference and pressure-rise from ambient atmospheric pressure are much dependent on the working current, our investigation was concerned with developing a capability to model free-burning argon arcs and considering the energy flux going into the anode at various values of the electrical current (I = 50, 100 and 200 A) by computational fluid dynamics analysis. Predicted temperatures along the z-axis between the electrodes were in fair agreement with existing experimental results. Particularly, reasonable relationships between the maximum velocity or temperature and the applied current were predicted, which matched well with other theoretical results. In addition, some discrepancies with other predictions were shown in the results about electric potential and pressure-rise. It should be related to the omission of the space-charge effect near the electrodes for a simplified unified model and the application of a turbulence model for the steep temperature gradient at the arc edges.