Experimental characterization of primary breakup in an air-swirl-assisted liquid jet atomizer

A novel atomizer utilizing air-induced swirling flow has been experimentally tested to enhance the breakup of high-inertia liquid jets into ligaments and droplets. The tangential swirl generates centrifugal forces that thin the liquid film and promote radial dispersion. The liquid exits the nozzle at high velocity, accompanied by superimposed swirl and shear, resulting in finer droplet formation. Primary breakup dynamics were captured using high-speed imaging under a range of liquid-to-gas Weber number ratios (0.3–42). Key stability parameters - including interfacial wave growth rate (0.035–0.08 m/s), breakup frequency (26.5–80.2 Hz), critical wavenumber (354.6–645.9 rad/m), and breakup length (0.05–0.41 m)-were quantitatively extracted. Improved empirical correlations for these parameters were established within the tested Weber number range. Compared to parallel-flow air-assisted atomizers without swirl, the swirling configuration demonstrated superior breakup efficiency, even at high liquid velocities.