Effect of vortex gas on the anode arc attachment behaviour inside the plasma torch: Numerical study

The arc behaviour within a vortex stabilised argon plasma torch is investigated by a transient fluid dynamic modelling. The simulation was carried out to mimic a plasma torch operating at a current of 200A, and the gas flow rate in the range of 5 and 15 slpm. Simulations show that the gas flow rate has a major impact on the arc attachment behaviour on the anode surface. At low gas flow rates a diffusive arc attachment is observed on the anode surface, however increasing the gas flow rate changes the attachment to partially diffusive or single spot. Higher gas flow rates increase the thickness of the cold boundary layer around the anode giving a high resistance for diffusive current transfer thus consolidating the current within a narrow column and consequently creating a spot attachment on the anode.