Experimental study of flash-boiling spray characteristics and unsteady dynamics in transverse crossflow

With the development of aero-engines toward higher thrust-to-weight ratios and the widespread use of regenerative cooling, fuel inevitably undergoes flash-boiling injection in the high-temperature, low-pressure environment of afterburners. Compared with subcooled liquid jets, flash-boiling sprays exhibit markedly different atomization characteristics and unsteady dynamics, yet the underlying transition mechanisms remain insufficiently understood. In this study, high-speed imaging was used to investigate the spray behavior of RP-3 aviation kerosene in a simplified non-reacting high-temperature low-pressure transverse-flow environment relevant to certain afterburner fuel-injection features, combined with time-averaged analysis, standard deviation statistics, and proper orthogonal decomposition (POD). The results show that flash boiling leads to a significant increase in spray cone angle due to phase-change-induced volumetric expansion. While the penetration depth increases nearly linearly with injection pressure under subcooled conditions, it levels off under flash-boiling conditions due to reduced droplet size and rapid momentum dissipation. POD analysis reveals a transition of spray unsteadiness from crossflow-induced large-scale vortical structures to phase-change-dominated small-scale breakup. These findings provide insights for spray stability optimization and nozzle design in afterburner applications.