Nozzle clogging seriously affects the continuity of spraying powder in vacuum induction melting gas atomization (VIGA) process and increases the consumption of gas and raw materials. However, there are few systematic studies on nozzle clogging. This paper reports the physics of nozzle clogging in gas atomization production. The influence of coupling-length of different melt delivery-tubes on nozzle clogging is studied numerically and experimentally. The interface tracking method of Volume of Fluid (VOF) and the large eddy simulation (LES) model are performed for visualizing the melt droplets flow traces in primary atomization and the associated simulation cloud images compared with experimental results. Four delivery-tube coupling-lengths (0 mm, 3 mm, 5 mm, and 7 mm) relative to nozzle position and two gas pressures (3 MPa and 4.5 MPa) are chosen for this study. The results indicated that the coupling-lengths of 0 mm and 3 mm increases the strength of the recirculation zone, the melt droplets backflow is obvious, and the nozzle is blocked. However, this phenomenon eliminated with increasing coupling-lengths, the atomization process is continuous, but the final fine powder yield decreases. This research is of guiding significance and reference for understanding the nozzle clogging of vacuum induction melting gas atomization (VIGA) technology.

Electrode induction melting gas atomization (EIGA) is a newly developed method for preparing ultra-clean metal powders, and is a completely crucible-free melting and atomization process. Based on conducted several atomization experiments, we found that the fine powder yields obtained during the EIGA process were greatly affected by the status of metal melt flow. While, continuous metal melt flow was beneficial for the yield of fine powders, it was in conflict with the principle described for the vacuum induction melting inert gas atomization (VIGA) process. To understand the critical role of continuous metal melt flow in the EIGA process, a computational fluid dynamics (CFD) approach was developed to simulate the gas atomization process. The D50 particle size of powder prepared by atomization under continuous liquid metal flow was about 70 μm, while that obtained by atomization under non-continuous liquid metal flow was about 100 μm. The diameter distribution results of numerical simulations agreed well with the experimental measurements, which demonstrated the accuracy of our simulation method. This study provides theoretical support for understanding the critical role of continuous metal melt flow and improving fine powder yields in the EIGA process. PACS: 02.60.Cb; 43.28.Py; 41.20.Gz; 81.20.Ev