Effects of Orifice Internal Flow on Liquid Jets in Subsonic Crossflows

Abstract

The effects of orifice internal flow on the spray plume characteristics of the liquid jet injected perpendicularly into subsonic crossflows were investigated experimentally. The internal flows are classified into threemodes: steady flow, cavitationflow, andhydraulic flipflow.Thesemodes aremainly determined by the ratio of the injector lengthL to the injector diameter d and by the shape of the orifice internal edge. To study the spray plume characteristics corresponding to each mode, three measurement techniques were applied: mass-flow-rate measurement, direct photography of internal injector orifices, and planar liquid laser-induced fluorescence. From the results of themassflow-rate measurement and direct photography, each mode of orifice internal flow without air crossflow was classified through the discharge coefficient patterns and internal–external flow shape. Steady flow shows no significant change on the flow pattern, and the discharge coefficient increases as the pressure differential increases. However, unsteady flows, including cavitation and hydraulic flip, have strong bubble envelopes due to a sudden reduction of flow passage, and these phenomena affect the discharge coefficient patterns. The penetrations and the width of the liquid spray plume were analyzed using the images obtained from the planar liquid laser-induced fluorescence method, and they were compared with the previous results. The penetrations and width were formulated with the liquid–air momentum flux ratio q and the ratio of the distance from the injector exit to the injector diameter x=d. It is found that the spray plume trajectory is determined by the liquid column diameter of the orifice exit and the liquid–air momentum flux ratio using the jet velocity at the orifice exit. It is also found that it is better to use the nominal parameters in the case of cavitationflow, and it is better to use the effective parameters in the case of hydraulic flip flow.