The width correlation of flash boiling jet considering cavitation effects and aerodynamic instabilities

Cavitation and flash boiling may coexist concurrently during depressurization conditions, and the interplay between cavitation and flash boiling remains incompletely understood. In this study, experiments and numerical studies were conducted to investigate cavitation evolution and its effects on flash boiling, and the jet width near the nozzle exit was extracted for quantitative analysis. The contributions of cavitation nucleation process to jet width were captured via a high-speed camera using the diffused back illumination method, with a focus on the near-field jet width. Simulation results and theoretical analysis were used to correlate the cavitation behavior and jet width. A correction in the exponent term in the nucleation barrier was achieved to account for the lower formation energy required for nucleation due to the presence of cavitation. Besides providing the nucleation sites, cavitation intensities and their fluctuation also contributed to the variations in jet width. Thermal effects on cavitation evolution began to manifest with the jet evolution. The modified cavitation number was proposed to account for the effects of injection pressure under non-flash and flashing stages. The deviation in the choked state induced by injection was not sufficient to account for the linear decrease in jet width, and thus a residence time term was introduced. Another pressure term was also introduced to account for the complicated role of ambient pressure in jet expansion. A comprehensive correlation containing the correction in nucleation barrier and aerodynamic instabilities was finally proposed and validated, providing guidance for the modulation of flash boiling based on cavitation evolution.