Numerical Study on Flow Induced Vibration of LOX Post in Liquid Rocket Engine Preburner.pdf

Numerical Study on Flow Induced Vibration of LOX Post in Liquid Rocket Engine Preburner Chihiro Inoue 1 , Toshinori Watanabe 2 and Takehiro Himeno 2 1 School of Engineering The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan E-mail: inoue@aero.t.u-tokyo.ac.jp 2 Department of Aeronautics and Astronautics The University of Tokyo ABSTRACT In a preburner of liquid rocket engines, some liquid-oxygen (LOX) posts, which introduced oxygen into combustion chamber, experienced severe flow-induced vibration due to unsteady cryogenic hydrogen flow. The mechanism of the vibration has not been fully understood because of the complexity of the flow field. In the present study, a new numerical method was developed to analyze the flow field of hydrogen, whose characteristic properties lie in its non-idealness and compressibility. The unsteady hydrogen flow inside the preburner unit was analyzed to investigate the details of hydrogen flow field as well as the mechanism of LOX post vibration. It was clarified that hydrogen flow inside the manifold and fluid dynamic forces on LOX posts were strongly affected by vortices shed from the junction at the upstream of the inlet. A baffle plate put inside the manifold was shown to reduce unsteady fluid forces on the LOX posts. INTRODUCTION In liquid rocket engines, a preburner is equipped at an upstream position of turbines to generate combustion gas for driving turbo pumps. A lot of liquid-oxygen (LOX) posts are arranged in the preburner to lead oxygen and hydrogen into the combustion chamber. A combustion chamber unit, schematically shown in Fig.1, is mainly consisted of a hydrogen manifold, an oxygen manifold, hundreds of LOX posts, and a combustion chamber. Figure 2 shows a cross-sectional view of hydrogen flow channel projected on the plane A-A’ in Fig.1. During the development of Space Shuttle Main Engine, some LOX posts were reported to experience harmful flow in