Electric arc I–V modeling and related plasma spectrometry issues

Abstract

This article is devoted to studying the properties of an electric arc column as a development of the authors’ early pioneer experiments. The object of modeling is a free-burning electric arc between evaporating copper electrodes in atmospheric air as the basis for the functioning of many modern technologies. It includes the determination of fundamental characteristics, such as the radial structure, and the current–voltage characteristics of the electric arc column under the assumption of plasma equilibrium. The middle cross section between the electrodes of a spheroidal shape arc is considered in order to limit the problem to a one-dimensional cylindrical approximation. It is strictly solved from the Elenbaas–Heller energy equation, with no resorting to the simplified channel model. The radial structure of the electric arc column is carefully considered with known temperature functions of electric and heat conductivities. Convenient functional approximations depending on temperature are proposed for the mentioned coefficients of copper–air plasma. The boundary between the arc column and atmospheric air is strictly located taking into account the chemical processes in the plasma of the copper–air mixture. The paper also presents some bases features of high-speed plasma spectrometry, substantiating the reliability of the obtained experimental data. As shown, the non-monotonicity of the current–voltage characteristics can arise due to the non-monotonicity of thermal conductivity as a function of temperature. Also, the loss of energy with the so-called ionization energy diffusion is insignificant in the overall energy balance of the arc. The results of the numerical simulation are compared with the experimental data.