Experimental study on the spray pattern and the merging process of dual-layer rotating conical liquid sheets

To comprehensively deepen the understanding of the primary breakup mechanism of dual-layer rotating conical liquid sheets, the spray field of a dual-orifice pressure-swirl atomizer was photographed using a high-speed shadowing method. The relationship and mechanism of the influence of the pressure-drop change of primary and pilot flow channels, and dual-layer liquid sheets merging on spray morphology, spray cone angle, and liquid sheet surface fluctuations were investigated in detail based on the analysis of spray field pictures. Attention was focused on the disturbance wave-change mechanism of the dual-layer liquid sheet merging process. The study shows that changing the pressure drop in the primary and pilot flow channels lead to changes in spray pattern, spray cone angle, and liquid sheet surface fluctuations. Furthermore, the influence of pressure drop in the primary flow channel is dominant, and the change in liquid sheet surface fluctuations is related to the spray pattern. In the process of liquid sheet merging (after the inner liquid sheet reaches the expected spray cone angle) the spray cone angle of the outer liquid sheet reduces in size, and only after the dual-layer liquid sheets are in contact with each other do the amplitude of the surface fluctuations of the liquid sheet become significantly larger and generate more medium- and high-frequency scatter.