Characteristics of internal and external flow fields and the atomization mechanism of air-assisted atomizing nozzles determined by large eddy simulation and experiments

Respirable dust in coal mines poses a severe health risk, and effective suppression remains a critical challenge. While air-atomizing nozzles are promising due to their production of fine droplets, their atomization mechanism is poorly understood, hindering the optimization of dust control strategies. This study bridges this knowledge gap by integrating experimental and numerical simulation methods to investigate the atomization process within the nozzle's mixing chamber and the near-nozzle region. Our results reveal that increasing air supply pressure intensifies fluid fragmentation and shortens the liquid jet breakup length. The key mechanism identified is the formation of coaxial ring vortices, which penetrate the liquid jet from its tip, causing core instability and primary breakup. Experimentally, we found that atomization angle initially increases then decreases, droplet size consistently reduces, and droplet velocity increases before stabilizing with higher pressure. By combining these insights, an optimal air supply pressure of 0.4 MPa was determined and validated in a field test at a fully mechanized mining face transfer point. This setting achieved a respirable dust suppression efficiency of 92.07 %, demonstrating a highly effective solution for mitigating hazardous dust pollution. This work provides both a fundamental understanding of air-atomization and a practical guideline for optimizing spray systems in coal mines.