Effects of particle loading on a reduced pressure inductively coupled radio frequency plasma torch

Abstract

Our previous attempts in the modeling of the heat transfer and fluid flow in radio frequency (RF) plasma torches considered dilute particle-loading conditions. It was assumed that the injected particles have no effect on the plasma temperature and velocity profiles. However, in practice, the plasma deposition process is carried out under fairly high loading conditions to achieve high energy efficiency. The plasma gas experiences significant local cooling and deceleration due to high particle injection rates. To this end, a numerical model has been developed which considers the coupling effects between the plasma temperature and velocity fields and injected particles. In this study, effort has been focused on the particle-loading effect in an inductively coupled RF plasma torch under a reduced pressure environment. The temperature and flow fields in an inductively coupled RF plasma torch are solved using an axisymmetric, variable property formulation of the Navier-Stokes equations. Pseudo two-dimensional electrical and magnetic field equations were considered. In addition, an integral constraint condition is used to maintain a specified discharge power in the plasma torch. The interaction between the plasma gas and injected particles is considered using the well-known “Particle-Source-In-Cell” (PSI-Cell) method. The exchanged mass, momentum, and energy between the plasma gas and injected particles are accounted for through additional source terms in the governing equations. The effect of particle loading on the resulting torch flow, thermal profiles, and particle-melting characteristics are presented and discussed.