Comparative analysis on spray characteristics of three pressure nozzles in high-speed crossflow

This study presents a systematic investigation into the transverse spray dispersion characteristics of three pressure nozzles, a self-excited sweeping nozzle, a plain-orifice nozzle, and a hollow-cone swirl nozzle, under high-speed crossflow conditions at Mach number 0.4. Initial characterization of their fundamental atomization performance was conducted in quiescent air, followed by spray field visualization in high-speed flow using planar laser Mie scattering imaging to quantify transient spray structures and time-averaged droplet concentration distributions. The results show that the self-excited sweeping nozzle demonstrated intermediate atomization performance between plain-orifice nozzle and hollow-cone swirl nozzle in quiescent environment. In high-speed crossflow, however, the self-excited sweeping nozzle achieves a 67% greater maximum penetration depth than the swirl nozzle and reaches 79% of that of the plain-orifice nozzle, and its spanwise spread distance matches the swirl nozzle, both 150% exceeding the plain-orifice nozzle. Assuming a rectangular spray distribution area, the total coverage area of the self-excited sweeping nozzle is 1.67 times that of the swirl nozzle and 2.17 times that of the plain-orifice nozzle. Moreover, the high-concentration droplet regions in both the central and lateral cross-sections of the self-excited sweeping nozzle are significantly larger than those of the other two nozzles, demonstrating superior spray uniformity. This study preliminarily confirms the unique advantages of the self-excited sweeping nozzle in enhancing spanwise diffusion, total spray coverage, and distribution uniformity in high-speed airflow environments. These findings provide a novel technical solution for liquid injection applications under high-speed airflow conditions such as scramjet/afterburner combustors and jet precooling systems.