PHYSICAL AND MATHEMATICAL-MODELING OF NON TRANSFERRED PLASMA TORCHES

The main objective of this work is to obtain temperature and velocity profiles of the plasma jet, including the electric are region, generat ed by non transferred plasma torches. The profiles are obtained from a numerical solution of the conservation equations which were used to d escribe the plasma flow. This modeling approach will help the developm ent and optimization of plasma torches, saving time and reducing costs of an alternative empirical development; it could also give some insi ght on the phenomena occuring inside the torch. Fluid mechanics models for laminar and turbulent flows were adopted to simulate the plasma i nside and outside the torch. Patankar's control volume method was chos en to solve the resulting coupled differential equations. The method i s very stable and requires less computational time than higher order m ethods, although it can be less accurate for some applications. A comp uter code was developed to simulate the jet flow of a plasma torch. Th e results obtained from this program compared very well with published ones, corroborating the assumptions of the present model and the nume rical method. Temperature and velocity profiles for a plasma torch wit h dimentions and operating conditions similar to the ones used in indu strial applications of spraying were generated and analyzed. The plasm a torch simulated had an electric are of 100A, plasma gas flow rate of 20 l/min, cross section of 5.2mm and anode length of 13mm.