Abstract: To understand the dynamic characteristics of the kerosene swirl injector in the pre-burner of the staged combustion LOX/kerosene rocket engine, dynamic characteristics in the open-end swirl injector with thick liquid film have been investigated experimentally. Using water as the working fluid, liquid films of different levels of thickness are obtained by changing the diameter of the tangential orifices of injectors. A flow pulsation generator is used to produce mass flow rate and pressure fluctuations in the feed line. The fluctuations of the pressure before injection are detected by a dynamic pressure sensor, and the dynamic response of the internal flow in the swirl chamber and the spray process are obtained by a high-speed camera. It is found that with long disturbance waves, the film thickness in the swirl chamber and the spray angle varies periodically, and at this moment there is little difference in the dynamic response between the thick and thin film injectors. With the decrease of disturbance wavelength, a portion of film with a "neck" is presented in the swirl chamber. The "neck" is propagated downstream, inducing the Klystron effect of spray after leaving the injector. When the disturbance wavelength was short, the disturbance waves are dissipated weaker in the swirl chamber with the thick film injector than with the thin film injector. However, the spray process of the thick film injector is not sensitive to any disturbance.

Key words: open-end swirl injector, thick liquid film, dynamic response, disturbance wave, Klystron effect, dissipation