Computational analysis of the influence of process parameters on the flow field of a plasma jet

A computational analysis has been carried out to simulate the temperature, velocity and air content of a plasma jet by using a computational fluid dynamics (CFD) code. Simplified models based on energy and mass conservation were used to link the velocity and temperature at the nozzle inlet with the operating conditions and this is shown to avoid the need for a complex chemical reaction model. The temperature, velocity and composition of the plasma jet were predicted by computational modelling and the results are in agreement with experimental data in the literature. The model takes into account the type and composition of the plasma gas through the specific values of the gas properties and their variation with temperature. The analysis includes a discussion of the effect of mesh size and the most appropriate type of turbulence model to be applied. To widen the generality of the predicted profiles, the temperature and velocity functions were expressed in a normalized form. It was found that in most cases the normalized functions were not significantly affected by the process parameters, such as are power and gas flow rate. As a result, these functions can be used to predict temperature and velocity providing their values at the nozzle exit are known. Further work showed that the accuracy of the predictions using the normalized functions is acceptable. This paper provides master curves and contour diagrams for predicting temperature and velocity profiles of the plasma jet as a function of the operating conditions. (C) 2000 Elsevier Science S.A. All rights reserved.