3-D numerical analysis of powder injection in various ICPT configurations

In this paper, numerical simulations of the trajectory and heating history of powders injected through a carrier gas in inductively coupled plasma torches working at atmospheric pressure have been performed within a fully 3-D FLUENT-based model [1-3], taking into account the effects of plasma-particle interaction. Continuity, momentum and energy equations are solved for optically thin plasmas under the assumptions of LTE and laminar flow, while an extended grid model is adopted for the treatment of the electromagnetic field. Simulations are performed over a network cluster of double processor calculators in order to use the full capabilities of the 3-D modelling. Due to the large memory and computational power granted by parallel processing, the gas injection section of an industrial TEKNA PL-35 plasma torch is included in the model without geometry simplifications. Particles are fed both axially, with injection velocity equal to that of the carrier gas, and radially, at the exit section of the torch; they are assumed to be spherical with no internal temperature gradients. Particles trajectory and thermal history are obtained by solving the motion and energy balance equations, respectively, also accounting for particle evaporation effects, as done in [4], with the final aim of putting into evidence the importance of a 3-D treatment of the problem for particular working conditions of the torch within various injection procedures. Computational domain for the particle tracking is here extended also downstream the torch region in order to simulate powders behaviour at the exit of the system, so allowing one to suitably design the reaction chamber typically used in this kind of induction plasma processing of materials [5]. Numerical results are presented for different particle materials, diameters and mass feed rates, using both pure Ar and Ar/H2 mixtures as plasma gas, under different working conditions of the torch.