Experimental investigation on the spray characteristics of an internal-mixing twin-fluid nozzle in crossflow

This study examined the spray characteristics and droplet behaviors of an internal-mixing twin-fluid nozzle operated in a crossflow environment. Although such nozzles have significant potential for various industrial processes, particularly under crossflow conditions, the overall flow structure, particularly in the downstream region, has not been fully explored. Accordingly, the gas-to-liquid mass flow ratio (GLR) and the crossflow Reynolds number (Re_c) were varied, and the entire flow field was captured using particle image velocimetry and a shadowgraph technique. The results showed that changes in GLR and Re_c lead to significant differences in the spray characteristics and droplet behavior. Higher GLR or Re_c yields a finer but less penetrating jet core, a thinner shear layer, smaller characteristic droplet diameters, and a lower peak Reynolds shear stress, whereas a lower GLR at a given Re_c produces a coarser spray, deeper penetration, and stronger turbulence generation along the jet boundary. Mean velocity and vorticity fields, the Okubo–Weiss (OW) parameter, and the Reynolds shear stress τ were analyzed to document where strong shear and vortical motions arise in a twin-fluid spray in crossflow. The velocity field shows jet deflection and a high shear band between the maximum penetration and center lines. The vorticity field exhibits coherent regions that weaken downstream. OW highlights strain-dominated bands along the upper shear layer edge, and τ is largest near the jet boundary in the near field. Droplet statistics at the downstream trajectory location indicate that D_max decreases with increasing GLR and Re_c, while farther downstream localized coalescence-driven regrowth is observed, yielding modest increases in droplet size. These results provide compact, measurement-based maps of flow organization and droplet sizes within the measured domain. This study provides indicators of shear and vortical structures and droplet response in crossflow and, within the measured range, reports how the GLR and Re_c affect the spray characteristics of a twin-fluid nozzle. These findings may inform operating-condition selection for similar twin-fluid crossflow systems.