Secondary atomization and solidification of metal melt in gas atomization

A gas atomizer is a device used to disperse a stream of molten metal into fine powder particles. Understanding and optimizing the atomization of metal powders are essential steps to enhance the quality and performance of AM-produced components. The breakup of the molten metal can be divided in two stages, primary and secondary atomization. In the primary stage, the liquid jet disintegrates into ligaments and larger droplets. The secondary breakup involves the fragmentation of these larger droplets into finer particles. In this secondary stage, the droplet breakup to fine particles and then cools down to solid state before reaching the bottom of the atomization chamber. The core objective of the thesis is centered on the modelling of the process of secondary breakup followed by solidification within a gas atomizer, using the lagrangian solver available in the open-source CFD software "OpenFOAM." The project consists of two key phases. In the initial phase, the focus lies on modelling and validating the secondary breakup of a liquid metal droplet. This involves integrating the Taylor Analogy Breakup (TAB) and implementing the Kelvin-Helmholtz (KH) mechanism, following the model described by Liu et. al \cite{Liuetal}. The validation model is based on Benz UCF-I test fuel (SAE J967d). Further modeling on solidification is conducted with iron, and its properties have been added to the software's thermodynamic library. As there is no available class/solver to handle the solidification of the broken-up droplets, the second phase involves developing a novel class within Lagrangian library for such modelling to transition the phase of liquid droplets to solid ones. This new class draws from the investigated phenomena and the derived equations concerning solidification and recalescence from the literature.