Search

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.

The main interest in the current study focuses on the possibility of overspeeding for the gas-generator cycle air turbo ramjet (GG-ATR) engine. The authors developed the air turbo ramjet engine and investigated its compressor performance. Based on those data, the authors developed the analytical code for the air turbo ramjet engine, which calculates the performances of turbomachinery, gas-generator, and ram combustor. The previous study described that the rotor overspeeding would not occur in the air turbo rocket engine. However, the current results show that degraded ram combustion can decrease the compressor pressure ratio and the compressor power. This reduced compressor power can cause overspeeding for the air turbo ramjet engine. The experimental results of compressor power and turbine inlet pressure support those analytical results.