Nonequilibrium simulation analysis of the power dissipation and the pressure produced by TIG welding arcs

The recently developed novel nonequilibrium model of TIG arcs is applied to study in detail the momentum balance and pressure establishment in the arc region and the power balance of the whole arc system. TIG configurations with two currents (100 and 200 A), two different cathode shapes (2-mm radius and vertex angles of 60 degrees and 30 degrees), and an electrode distance of 5 mm are considered exemplary. The pressure analysis yields two regions of pressure in excess of atmospheric pressure below the cathode tip in front of the anode. The maximum values show weak dependence on the cathode vertex angles. The growth of the arc pressure with the arc current is predicted to be faster than quadratic. The analysis of the power budget shows the importance of the Joule heating term in the electron energy balance, which is the dominant mechanism in the vicinity of the cathode and the near surrounding while it is negative in the vicinity of the anode. The electric power deposited in the cathode space-charge sheath is a huge amount of the total power supply (40% at 200 A and 50% at 100 A) with a significant part of it being transferred to the plasma electrons.