Optimization of water nozzles for gas–water combined atomization: Study on water film characteristics

Based on computational fluid dynamics simulations, this study is motivated by the need to improve water film stability and cooling efficiency in the spinning water atomization process. A gas–liquid two-phase flow model, coupling the shear stress transport k–ω turbulence model with the volume of fluid multiphase approach, was established to systematically investigate how key structural parameters of the water nozzles (number, diameter, inclination angle, shape, and arrangement) affect the formation characteristics of a high-speed swirling water film. The results identified an optimal nozzle configuration, which was then applied to the gas–water combined atomization process for preparing Fe-based amorphous powders. Under a fixed total water flow rate of 40 tonnes/h, the number and diameter of nozzles are found to be critical factors governing water film uniformity and kinetic energy. To quantitatively evaluate the thickness uniformity of the swirling water film, a uniformity index U is proposed, defined as the standard deviation of film thickness normalized by its mean value. A smaller U indicates a more uniform and stable film. A “tangential-type” nozzle design significantly reduces flow resistance and enhances film stability and velocity, while a vertical nozzle arrangement improves the flow path, yielding a more uniform film thickness and better momentum retention in the middle and lower sections. The optimal combination of four nozzles (10 mm diameter, tangential shape, and vertical arrangement) produced a uniform water film thickness (13.9–35.2 mm) and moderate velocity (maximum 54 m/s), providing favorable conditions for secondary melt fragmentation and rapid solidification. The optimized configuration achieves the lowest uniformity index of U = 0.331, confirming the improved film homogeneity. Industrial trials using this optimized configuration demonstrated a strong capability for producing amorphous alloy powder. These findings provide a theoretical and practical foundation for enhancing water film stability in gas–water combined atomization systems, thereby advancing the efficient manufacture of high-performance amorphous powders.