Three-dimensional modelling of the characteristics of long laminar plasma jets with lateral injection of carrier gas and particulate matter

Abstract

A long laminar plasma jet has adjustable high-temperature region length, small temperature and velocity gradients in the axial direction, low noise emission and weak entrainment of ambient air into the jet, and thus it has potential applications in materials processing. A three-dimensional modelling approach is used in this paper to study the spatial distributions of plasma parameters in the long laminar plasma jet for the case with and without lateral injection of particulate matter and its carrier gas. The combined diffusion coefficient method is employed in the modelling to treat the diffusion of ambient air into the plasma jet. Typical computed distributions of temperature, velocity and species concentration in the jet are presented using the long laminar argon plasma jet issuing into ambient air as a calculation example. It is shown that similarly to the turbulent plasma jet case, the long laminar plasma jet has good enough stiffness to endure the impact of the laterally injected carrier gas, although the laminar jet assumes slight deflection from its original geometrical axis in the injection plane due to the action of laterally injected carrier gas. The three-dimensional effects caused by the lateral carrier-gas injection on the jet characteristics and thus on the particle moving trajectories and heating histories are shown to be appreciable. Particulate matter can be fed into the high-temperature region of the laminar plasma jet with the aid of the carrier gas.