CFD modelling of Close-Coupled Gas Atomisation (CCGA) process by employing the Euler-Lagrange approach to understand melt flow instabilities

• Published in: Chemical engineering science 2024-08, Vol.295, p.120205, Article 120205
• Main Authors: Samuel J, Jo, Mullis, Andrew M., Borman, Duncan J.
• Format: Article
• Language: English
• Subjects: Close-Coupled Gas Atomisation (CCGA); Compressible flow; Computational Fluid Dynamics (CFD); Discrete-Phase Model (DPM); Euler-Lagrange approach; User-Defined Function (UDF)
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2024.120205

[Display omitted] •Novel approach of coupling aspiration pressure and the melt mass flow rate.•Flow-field showed continuous fluctuations only at lower gas-to-melt ratios (GMRs).•Fluctuations of multiple frequencies seen in amplitude modulation.•Gas flow-field fluctuation associated to alternation of wake condition.•The continuous fluctuation seen in the flow field was evaluated to be 8.1 kHz.•Open- to closed-wake condition corresponded to melt flow fluctuation. This paper presents a CFD analysis of the melt and flow-field instabilities in a close-coupled gas atomisation process (CCGA) caused by the gas–melt interactions. The melt mass flow is coupled to the atomiser internal pressure, which varies over time due to the unsteady flow field. A two-phase flow of Argon gas and melt particles is modelled using a coupled Euler-Lagrange framework. Three different initial gas-to-melt ratios (GMRs) of 5.5, 2.6 and 1.32 are considered to study the gas–melt interaction. The results show that in the case GMR = 1.32, sustained instability both in the melt and in the flow-field are distinctly observed, resembling physical atomisation process. This melt fluctuation corresponded to an alternating flow-field fluctuation; alternating between open- to closed-wake condition, where the local maxima of the melt corresponded to an open-wake condition, and the local minima of the melt corresponded to a closed-wake condition.