Analysis of Chemical Nonequilibrium and Elemental Demixing in Plasmatron Facility

摘要

A detailed numerical analysis is performed in the torch and in the test chamber of an inductively coupled plasma facility. The main purpose is the analysis of the plasma jet in the test chamber and the assessment of its degree of nonequilibrium together with the level of elemental demixing. To this end three different mathematical formulations have been used: an extended chemical nonequilibrium formalism including finite-rate chemistry and two forms of equation valid in the limit of local thermochemical equilibrium, i.e. the equilibrium formulation with variable elemental fractions, which takes into account the demixing of chemical elements and the classical formulation, where the molar fraction of elements is supposed to be constant. To assess the influence of the finite-rate chemistry model on the results, two models have been used. Simulations at various operating pressures indicate that the model dependency is strongly reduced at sufficiently high pressures (above 10 kPa) while relevant at lower pressure. As the operating pressure is increased, chemistry becomes increasingly fast and the nonequilibrium results correctly approach those obtained assuming local thermochemical equilibrium, provided that elemental fraction variations are correctly taken into account.