ロケットエンジン用ターボポンプの入口配管の音響効果を考慮したキャビテーションサージの一次元解析 : 第1報,変動周波数の不連続性(流体工学,流体機械)

Abstract

In a liquid rocket engine, cavitation in the inducer of a turbopump sometimes cause instability phenomena when the inlet pressure of the inducer is decreased. Cavitation surge, one such instability phenomenon, has been discussed mainly in connection with an inertia model. When such a model is used, the frequency of oscillation changes continuously as the inlet pressure decreases. However, we obtained interesting data on an experimental turbopump that showed that the surge frequency changed disconnectedly. With the aim of explaining this phenomenon, we conducted a one-dimensional analysis applying an acoustic model, combining the inlet pipeline with the sonic velocity of liquid oxygen. It was found that this phenomenon is a kind of self-excited vibration coupling the cavitation characteristics with the acoustic resonance of the inlet pipeline. Furthermore, as the inlet pressure decreases, the characteristic of the turbopump changes from a closed boundary condition to an open boundary condition, the frequency of the cavitation surge slightly decreasing.