Two-temperature chemically non-equilibrium modelling of high-power Ar–N2 inductively coupled plasmas at atmospheric pressure

Abstract

A two-dimensional thermal and chemical non-equilibrium model was developed for high-power Ar–N2 inductively coupled plasmas (ICPs) at atmospheric pressure, which are conventionally assumed to be under local thermal equilibrium condition. The energy conservation equation of electrons was treated separately from that of heavy particles. These equations consider reaction heat effects and energy transfer between electrons and heavy particles as well as enthalpy flow resulting from diffusion due to the particle density gradient. Chemical non-equilibrium effects were also accounted for by solving mass conservation equations for each particle, considering diffusion, convection and net production terms resulting from 30 reactions. Transport and thermodynamic properties of Ar–N2 plasmas were self-consistently calculated using the first-order approximation of the Chapman–Enskog method at each iteration using the local particle composition, heavy particle temperature and electron temperature. Power balance for the electron energy and the mass balance of atoms and ions in a high-power Ar–N2 ICP were investigated using the model developed. Calculational results obtained by the present model were compared with results from two other models such as a one-temperature chemical equilibrium model and a one-temperature chemical non-equilibrium model. This comparison supported the discussion of chemical and thermal non-equilibrium effects in the high-power induction plasma.