CFD Modelling of Closed-Couple Gas Atomisation (CCGA) Process.*

Eventhough gas atomisation process is the most viable method to produce metal powders, the process is chaotic, and extremely rapid, preventing a clear understanding of it. Due to this chaotic nature, the particle size and particle size distribution increases to a greater extent, making the process highly inefficient. Consequently, a huge amount of energy and capital is lost.

In this research, CFD analysis is carried out to understand the instabilities present between the deep sub-ambient pressure formed in front of the melt nozzle tip known as aspiration pressure and the melt flow rate. Rapid variations in melt flow rate caused due to the change in aspiration pressure affects the particle size and particle size distribution. A two-phase flow is modelled using coupled Euler-Lagrange framework. Primary phase is Argon; Secondary phase is modelled as inert, constant diameter particles depicting the melt. The particles’ mass flow rate is coupled to the aspiration pressure using User-Defined Functions. This research confirms the presence of a pulsating flow field as postulated by TIng(2003), exhibiting repeated formation and disruption of a Mach disk causing fluctuation in aspiration pressure, which explains the rapid variations in melt flow rate and the chaotic nature of the process.