Three‐Dimensional Modeling of Thermal Plasmas (RF and Transferred Arc) for the Design of Sources and Industrial Processes

Abstract

A three-dimensional (3-D) model for the simulation of inductively coupled plasma torches (ICPTs) working at atmospheric pressure has been developed at the University of Bologna, using the customized CFD commercial code FLUENT 1 . The helicoidal coil is taken into account in its actual 3-D shape, showing its effects on the plasma discharge for various geometric, electric and operating conditions without axisymmetric hypotheses of simplification. Simulations have been performed for Ar plasmas. The gas injection section of an industrial TEKNA PL-35 plasma torch is included in the model without geometry simplifications, refining the mesh at the injection points, in order to perform a more realistic simulation of the inlet region of the discharge, taking into account also turbulence effects. Metallic and ceramic particle axial injection in the discharge through a carrier gas by means of a probe is simulated as well, taking into account the energy and momentum transfer between the continuous and the discrete phases and the effect of particle turbulent dispersion. The behavior of transferred arc thermal plasma sources operating at atmospheric pressure for the treatment of a substrate material (for waste treatment purposes and for metallic substrate cutting or hardening) has also been investigated by means of a 3-D time-dependent numerical model, using a customized version of the CFD commercial code FLUENT 1 . Unsteady flow and heat transfer equations are solved with coupled electromagnetic ones, for an Ar optically thin plasma under conditions of laminar flow and local thermodynamic equilibrium (LTE). The transient effects of an imposed external magnetic field on the shape of the single torch arc are investigated. The importance of fully investigating plasma velocity and temperature fields in high-power twin torch transferred arc systems designed for waste treatment purposes is outlined with reference to a plasma source designed and operated by Centro Sviluppo Materiali (CSM SpA) in Castel Romano, Rome. All calculations have been performed using PlasMac, a cluster of workstations available at CIRAM & DIEM, University of Bologna, so allowing for a large reduction in computational time as well as for the treatment of complex computational domains otherwise not manageable with traditional personal computers.Advanced Plasma Technology. Edited