Experimental study on spraying mechanisms of the gas–liquid internal flow in an air-assisted nozzle

Air-assisted nozzles are widely used in many industrial fields. For example, in artificial snowmaking systems, air-assisted nozzles can provide a key promoting role for the nucleation and crystallization of snow. To reveal how spray behavior depends on the internal flow patterns of air-assisted nozzles, we designed an experimental platform to observe the two-phase flow inside the nozzle. The results show that the internal flow pattern of the nozzle exhibits an annular flow pattern, forming a continuous hollow conical spray. As the gas–liquid pressure ratio (GLRP) increases, the interfacial disturbance waves gradually disappear at the gas–liquid interface of the internal flow, indicating a transition from a more turbulent to a more stable flow regime. As the gas core expands, the liquid film thickness gradually decreases, promoting finer atomization and a more uniform droplet distribution. This transition from a disturbed wave pattern to a stable annular flow enhances the uniformity of the droplet distribution and the stability of the spray. When GLRP increases from 20% to 67%, the uniformity of droplet distribution improves by 17%, and the stability is enhanced by 60%. Additionally, this study examines the link between internal flow patterns and atomization, providing a dimensionless formula that correlates nozzle flow dynamics with spray quality based on experimental and simulation data. This contributes valuable insights for optimizing air-assisted nozzle design for superior spray performance.