Investigation of Transition Phenomenon from Rotating Cavitation to Attached Asymmetric Cavitation by Coupled Analysis of One-Dimensional Flow Path Model of 3-Blade Inducer and Shaft Vibration System

Purpose: During the development process of the turbopump for a rocket engine, various problems of shaft vibration have been reported. Among them, vibration problems caused by dynamic fluid flow phenomena in the inducer, such as rotation cavitation (RC) and attached asymmetric cavitation (AAC), are known to be major factors that impair the stability of the system. The transition from RC to AAC was observed experimentally, however, there has been no analytical investigation of this transition phenomenon. The Purpose of this study is explaining the transition from RC to AAC in the inducer. Methods: The fluid flow phenomena in the inducer was modeled using a one-dimensional flow-path model of the inducer. The representation of pump dynamic characteristic coefficients (cavitation compliance and mass flow gain factor) in each flow path was proposed and investigated. Furthermore, a coupled analysis of the rotor and fluid systems was performed to investigate this transition from RC to AAC in the inducer. Results: The occurrence of this transition from RC to AAC in the inducer was observed and explained. It was evaluated by comparison with the experimental results. Conclusions: The key factor of transition from RC to AAC in the inducer was the signs of the pump dynamic characteristic coefficients (both cavitation compliance and mass flow gain factor). Transition occurred when both were set as negative. The results of the coupled analysis were qualitatively in good agreement with the experimental results obtained from the water tunnel test.

Online Published: 06 March 2023