CFD study of gas-powder injection characteristics in a novel lance with supersonic shrouding jet

Abstract

Supersonic gas–solid jets are widely applied in the spraying coating processes, drug delivery, and metallurgical reactors, due to exceptional penetrating capabilities. In this study, a novel lance is designed to increase the penetration depth of gas–solid flow by utilizing a supersonic shrouding jet (SSJ). Subsequently, the numerical model based on the Eulerian-Lagrangian framework is applied to analyze the supersonic gas-powder flow within the lance. After validating the reliability of numerical model with experimental data, the gas-powder flow characteristics are discussed. The results indicate that the presence of SSJ enhances the powder velocity and penetration depth significantly by blending supersonic gas. Moreover, the particle-gas momentum interaction primarily occurs inside the central pipe and downstream of the lance exit. Along the radial direction, the particle dispersion is the result of the combined interplay between lift force and particle–particle collisions. The lift force enhances particle collision frequency, and these collisions, in turn, facilitate the conversion of axial momentum into radial momentum, resulting in substantial radial acceleration. When SSJ exits, the particle radial dispersion is constrained, primarily due to the reduced particle residence time. Additionally, the introduction of low-temperature oxygen from SSJ results in a reduction in both the carrier gas and particle temperatures. The results provide meaningful insights into understanding the supersonic gas–solid flow mechanisms of the SSJ lance.