Multiscale descriptions of particle-droplet interactions in multiphase spray processing

Composite particles are solid particulates that consist of two mixed material phases so that a dispersed phase is homogeneously distributed in the host matrix phase of each particle. Metal-matrix-composite (MMC) particles may be produced through mixing of ceramic particles and metallic droplets in a spray atomization and co-injection process. In this paper, multi-scale descriptions of particle-droplet interactions in spray processing of MMC particles are realized based on multiscaled Multiphase Computational Fluid Dynamics (M-CFD) models. On the macro-scale, the mixing configuration of solid-particle laden jets and liquid droplet sprays is investigated based on an Euler-Lagrange-Lagrange (ELL) method. The particle-droplet mixing degree in this stage is mainly influenced by the atomization gas mass flow rate through affecting droplet break-up (thereby droplet inertia) and droplet solidification rate. On the meso-scale, the particle-droplet collision probability and process between a metallic droplet and solid particles along the droplet trajectory is derived according to kinetic theory of gases and simulations based on the Lagrangian tracking. The collection efficiency of solid particles by a liquid droplet in this stage is derived as a function of droplet size and atomization gas pressure. On the micro-scale, the critical kinetic conditions for a solid particle to penetrate into a liquid droplet is derived based on the particle-droplet collision regime map by taking into account the variation of the droplet consistence in a solidifying droplet. The simulation results indicate that a large quantity of ceramic particles can be incorporated into the metal matrix particles or captured by the MMC-particle surfaces by optimizing the process configuration and the process operation conditions. It is shown that gas atomization of a melt with co-injection of particulates is a viable approach to generate MMC particles. (C) 2015 Elsevier Ltd. All rights reserved.