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

• Published in: Acta astronautica Vol. 154; pp. 82 - 91
• Main Authors: Cheng, Peng, Li, Qinglian, Kang, Zhongtao, Chen, Huiyuan
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.01.2019; Elsevier BV
• Subjects: Combustion instability; Droplets; Dynamic response; Flow velocity; Fluid dynamics; Image processing; Image processing systems; Injectors; Inner flow; Nozzles; Oscillators; Pressure oscillations; Pressure swirl injector; Proper Orthogonal Decomposition; Spray characteristics; Thin films; Two phase flow; Wave propagation; Dynamic response; Combustion instability; Inner flow; Pressure swirl injector; Spray characteristics
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/j.actaastro.2018.10.001

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. •The response of a pressure swirl injector to pressure oscillation is clarified.•The pressure oscillation inside the injector propagates in a long-wave manner.•Pressure oscillation leads to oscillation of inner flow, spray and size of droplets.