Effect of Dimensionless Numbers on Air Core Diameter of Pressure-Swirl Atomizer

Abstract

Air core is an important parameter in pressure swirl atomizer since formation of air core determines the thickness of the discharged liquid sheet and the effective flow area of nozzle discharge. This consequently will affect the coefficient of discharge and the spray angle. This study conducted for the investigation of the relation between dimensionless numbers on the air core diameter. Dimensionless numbers are helpful aid for the quantification of independent parameters involving atomizer design and operating conditions simultaneously. Reynolds number, Re and orifice-to-swirl chamber diameter ratio, N are the dimensionless numbers selected for this study. Despite of the availability of study on the effect of dimensionless numbers on air core diameter, more study requires especially for smaller N. An experimental test-rig was constructed to conduct the performance test of the atomizer. Acquired images were analyzed using image-processing software. It was found that N has more significant effect on the change of air core diameter compared to Re. However, it is observed that at Re = 40000, N = 0.07 produces almost similar air core diameter with N = 0.25 at Re < 20000. In contrast, with N = 0.5, air core diameter produces are larger even at Re < 20000. Hence, it can be concluded that both Re and N are important parameters in characterizing the air core diameter in pressure-swirl atomizer.