A Critical Analysis of Proposed Plasma Jet Models to Predict Temperature and Velocity Profiles

Abstract

ABSTRACTThe prediction of temperature and fluid flow associated with a d.c. plasma jet exiting from the nozzle has been an important issue for-some years. Modeling efforts have mainly relied on incompressible flow formulations and various turbulence models to predict the d.c. plasma at atmospheric conditions. The primary assumption of such models is that the plasma is in local thermodynamic equilibrium, steady state, and that no other species from the ambient are entrained. In the subsonic parabolic approach, the plasma is treated as a free jet with no downstream influence on the upstream calculations. The elliptic approach needs conditions to bespecified along all boundaries, and calculations are dependent on the extent of the solutiondomain and the exit boundary conditions.Very few attempts have been made to model plasma jets which are supersonic upon exiting the nozzle. The problem is important due to the advantages of low pressure plasma deposition but is complex and difficult to analyze. Specifically one has to acount for compressibility and viscous dissipation effects. Off-design operating conditions (over or underexpanded conditions) greatly influence and complicate the plasma temperature and velocity profiles.