3-D Flow Modeling of a Three-Phase AC Plasma Torch Working With Air Using a Stationary Source Domain With Gas Radiation

This computational fluid dynamics work is dedicated to the study of heat and mass transfer in a new 100-kW three-phase ac/50 Hz plasma torch operating with air. The transient behavior of the arc is simplified using time-averaged heat and momentum source inputs in a stationary source volume whose form was chosen according to the results from a separate magnetohydrodynamic calculation. A parametric study of source volume and momentum intensity is conducted and shows a little influence on the overall temperature and velocity fields. Radiation from gas and walls is taken into account using the discrete ordinate model. Air radiation data consider both atomic and molecular contributions in the temperature range between 300 and 30 000 K and for the wavelengths from 0.209 μm to the far infrared. The results show a huge impact of radiation on wall temperature and heat losses. Two different methods, Planck and Rosseland, are used for the calculation of mean absorption coefficients. Although Planck's average is recommended in this case, the absolute temperature difference between both averages is below 13%. Finally, this paper allows checking that the temperature of different components of plasma torch remains below the physical limits of the selected materials.