Test on self-excited oscillation characteristics of an open-end swirl injector with thick liquid film

To understand the self-excited oscillation characteristics of the kerosene swirl injector in the pre-burner of staged combustion LOx/kerosene rocket engine, self-excited oscillation in the open-end swirl injector has been investigated experimentally in the atmospheric environment using water as the working fluid. Sustained self-excited oscillation of the internal flow process was spontaneously generated in an open-end swirl injector with long swirl chamber and thick liquid film. The fluctuations of the pressure before injecting, the gas core in the swirl chamber and the spray process were detected by a dynamic pressure sensor and a high-speed camera. It is found that the gas core in the swirl chamber became disconnected periodically when self-excited oscillation was generated, and the Klystron effect of spray was induced when the gas core was disconnected. The fluctuation frequencies of the pressure, the gas core and the spray were close to each other under the same working condition, and were limited in the range from 10 to 45 Hz with different injection pressure drops. The pressure drop of the injector had unremarkable impact on the fluctuation process. There is a significant correlation between the relative amplitude of dynamic pressure and the fluctuation frequency. The self-excited oscillation of the injector may be induced by interaction of the gas core with the film in the swirl chamber. © 2018, Press of Chinese Journal of Aeronautics. All right reserved.