Effect of ambient gas density on spray characteristics of swirling liquid sheets

The spray and breakup characteristics of a swirling liquid sheet were investigated by measuring the spray angle and breakup length as the axial Weber number We(l) was increased up to 1554 and the ambient gas pressure up to 4.0 MPa. As the We(l) and ambient gas density p increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces, and thus the liquid sheet disintegrated from the injector exit. The measured spray angles according to the ambient gas density differed before and after the sheet broke up. Before the liquid sheet broke up, the spray angle was almost constant; however, once the liquid sheet started to break up, the spray angle decreased. As the ambient gas density and We(l) ncreased, the increasing aerodynamic force caused the breakup length to decrease. Finally, the measured breakup lengths according to the ambient gas density and We(l) were compared with the results of the linear instability theory. Considering the attenuation of sheet thickness in the linear instability theory, the corrected breakup length relation agreed well with our experimental results.