2-D and 3-D fluidynamic and plasma characterization of DC transferred arc plasma torches for metal cutting

The aim of this work is to investigate by means of a 2-D and 3-D FLUENT(C) based numerical model the behaviour of a transferred arc plasma torch recently developed within Cebora S.p.A. for the cutting of a metallic substrate material. Flow and heat transfer equations are solved with coupled electromagnetic ones, for LTE optically thin plasma, while turbulence phenomena are taken into account by means of a k-epsilon Realizable model. Simulations include a prediction of the thermal behaviour of the hafnium insert of the cathode and trajectories of hafnium oxide particles emitted from it and the efficiency of nozzle cooling systems in various operating conditions including gas mixtures (O-2/Air, H35/N-2, Air/Air) fitted for various dimension and type of the cutting material. Results obtained from the simulations are compared with experimental measurements in order to perform a validation of the model in terms of pressure in different regions of the device, gas mass flow rate and nozzle temperature during the processing phase. For this purpose a modified plasma torch has been designed and used with realistic cutting conditions.