Swirling supersonic gas flow in an EIGA atomizer for metal powder production: Numerical investigation and experimental validation

Abstract

This paper is concerned with the modeling of the Electrode Induction Melting Gas Atomization (EIGA) process. This process employs a swirling supersonic inert gas jet to atomize a free-fall molten metal stream, with the aim to produce powders of highly reactive metals. As a first step towards the development of a complete model, this study aims to describe the behavior of the swirling gas flow through and downstream the EIGA gas nozzle and to highlight the influence of the main operating parameters on the jet characteristics. The developed model is based on the Reynolds-Averaged Navier-Stokes (RANS) approach using the Favre decomposition for compressible flow together with a k-ω SST turbulence model. The numerical results are partially validated against images of the gas flow patterns obtained using the Schlieren imaging technique. The simulation results show that the gas flow transits to a supersonic regime immediately before exiting the nozzle. In the atomization tower, it forms a swirling supersonic jet with an asymmetric geometry composed of several Mach diamonds. The inlet gas pressure has a significant effect on the jet structure and Mach number distribution. However, within the investigated range of pressure values (30–45 bar), the swirling motion of the jet, hence the jet geometry, remain little affected. In contrast, a small increase of the nozzle exit slit size significantly increases the swirling motion, which in turn strengthens the jet asymmetry. A reduction of the overpressure in the melting chamber has a similar effect, but to a lesser extent.