Thermal Analysis and Digital Design for Non-transferred Plasma Processing

Direct-current (dc) non-transferred arc plasma torches have been widely used in the processing of metals and related oxides at atmospheric pressure. To optimize the torch structure for better performance on lifetime and thermal efficiency, a 2D axisymmetric, quasi-steady numerical model with multiple phases has been built and validated by the DC torch experiment. The results uncover that the arc inside the torch keeps moving during operation and its start position and moving distance are affected by nozzle length. The predicted peak temperature position on the anode wall by radial current density distribution is in good agreement with temperature distribution on the anode interior surface, which provides clues in the design of torch structure. For thermal efficiency, most power is wasted through a cooled anode wall, whereas a reasonable nozzle length could reduce the energy loss and improve the total input power to achieve better processing ability.