Response of inner flow and spray characteristics of a pressure swirl injector to pressure oscillation in supply system

摘要

The present work focused on the response of the two phase flow of a pressure swirl injector to pressure oscillation in supply system. A mechanical pulsator was used to generate pressure oscillation in supply system. The inner flow of the injector and spray were captured by backlit shadowgraph technique and the droplet size was recorded by laser diffraction technique. In addition, image processing and proper orthogonal decomposition were used to analyze the data. The results indicate that the inner flow, spray and droplet size oscillate along with pressure oscillation mainly at the driving frequency. The oscillation of air core was used to characterize the inner flow. The dynamics of air core center and air core diameter was analyzed and the modes of the inner flow were obtained. Then, the way the oscillation propagated inside the nozzle was identified as a long wave manner. When the liquid was emanated from the nozzle, thick film resulted from pressure peak was faster when compared with thin film resulted from the trough of pressure oscillation. This characteristic was found to be responsible for the sudden shrink of the spray, and changed the spray pattern from a hollow cone to a pagoda. Finally, the thick and fast film produced a dense spray and large droplets. The whole paper discussed the response of inner flow and spray characteristics of a pressure swirl injector to pressure oscillation, and revealed the way the pressure oscillation propagated from supply system to spray field.