Modeling of an AC Plasma Torch—Part II: Gasdynamic Pattern and Effect of Flow Rate

The article is the continuation of the work devoted to the numerical study of processes in the single-phase ac plasma torch operating at low current (up to 10A RMS). The main attention is paid to the analysis of the flow pattern and the behavior of gasdynamic parameters. The effects of flow acceleration and rarefaction of near axial arc core are shown. The effects of the transformation of gasdynamic structures typical for cold flow (e.g., vortex behind the back step), as well as the appearance of new structures (e.g., vortexes in the jet periphery), are demonstrated and discussed. An explanation is given for the effect of the increase of the arc voltage drop with the increase of the flow rate of supplied air, associated with the increase of the medium electric resistance. The presented results are in accordance with the experimental data on the voltage drop in a conventional ac plasma torch.