Abstract: To comprehensively deepen the understanding of the primary breakup mechanism of conical liquid sheets, this study numerically simulated the atomization process of dual-layer conical liquid sheets, focusing on the effects of pressure drop and coaxial rotating air on the primary breakup characteristics of the liquid sheet such as the macroscopic morphology of the dual-layer liquid sheet, the breakup mode and length of the liquid sheet, and the spray cone angle. The macroscopic morphology of the numerically calculated spray field was close to the experimental results, and the maximum errors of the numerically calculated spray cone angle and the Sauter mean diameter were 4.9% and 7.4%, respectively. The numerical results show that the participation of coaxially rotating air in the atomization will change the overall morphology of the spray field. With the increase of pressure drop and air velocity, the breakup mode and the dominant surface wave mode of the liquid sheet will be changed. The merging of the dual-layer of liquid sheets will produce drastic surface fluctuation on the surface of the liquid sheet, slightly increasing the spray angle. The breakup length of the liquid sheet decreases as the pressure drop and the axial velocity of the coaxially rotating air increase. This research facilitates further studies on the mechanisms of dual-layer liquid sheet primary breakup, thus providing guidance in the understanding of atomization in the double pressure swirl injector.

Key words: spray nozzles, primary breakup, breakup mode, surface fluctuation, spray pattern, breakup length