The effect of two-chamber electrode geometry on gas dynamics in an arc channel of plasmatorch

Abstract

Methods of 3D numerical simulation were applied for evaluating the flow dynamics in the internal electrode of a plasmatorch with a two-chamber design while a “cold” blowout through the electrode. This study presents spatial distributions for the gas flow velocity, turbulence kinetic energy and the pressure inside the two-chamber electrode equipped with two swirlers (they provide tangential input for plasma-forming air flow). Variations in the gas velocity for transversal cross sections of the arc chamber are in agreement with previously published data for the case of “cold” smoke-based blowout of the two-chamber plasmatorch equipped with a cylindrical electrode. It was established that the cylinder-conical shape of the internal electrode might result in a shorter initial laminar column in the electric arc; this happens due to expansion of the turbulent interval at a fixed length of the arc. Experiments in a plasmatorch with an inter-electrode insert demonstrated that the cylinder-and-cone shape of the electrode causes a higher (by 30–35 %) voltage on the plasmatorch as compared with the cylinder-only shape of the electrode. This is a qualitative confirmation for calculated results about a higher kinetic turbulence energy and a wider turbulent zone of the electric arc occurring in a two-chamber design plasmatorch.