A MODEL OF FLUID, HEAT-FLOW, AND ELECTROMAGNETIC PHENOMENA IN A NONTRANSFERRED ARC PLASMA TORCH

A mathematical model is presented to describe the electromagnetic, heat flow, and fluid flow phenomena within a nontransferred arc plasma torch and in the resultant plume. In the development of the model allowance is made for the conservation of mass, momentum, thermal energy, and the continuity of the current. An important, novel feature of the model is that it can predict both the pattern of heat generation within the torch and the electromagnetic forces, thus providing a fundamental basis for predicting plume behavior. Specific calculations are presented for a pure argon system (i.e., an argon plasma discharging into an argon environment), operating in a laminar mode, and the theoretical predictions appear to be in quite good agreement with experimental measurements. An important finding of the work is that the electromagnetic forces may markedly modify the velocity profiles and may significantly affect the swirl of the plasma gas exiting the torch. In addition, swirl is shown to have a significant affect on the behavior of the arc and thus affects the resulting plume.