Theoretical Analyses of Rotating Cavitation in Inducers

Abstract

Rotating cavitation (R.C.) is one of the most important problems in the development of modern rocket turbopump inducers (Kamijo et al., 1993, Goirand et al., 1993, Ryan et al., 1994). By 2-D linear analysis (Tsujimoto et al., 1993), rotating cavitation was found to be caused by the positive mass flow gain factor, namely, the increase of cavity volume due to the decrease of flow rate, and to be completely different from rotating stall (R.S.) which is caused by the positive slope of the head characteristic. Moreover, 2-D analysis predicted that there can be two modes of rotating cavitation: the forward rotating mode which propagates faster than the impeller, and the backward rotating mode which propagates in the direction opposite to that of the impeller. Nonlinear (Tsujimoto et al., 1996) and 3-D (Watanabe et al., 1997) analyses resulted in basically the same results as those obtained for the previous 2-D cases and predicted forward and backward propagating modes. These were reported at the last meeting of the conference (Tsujimoto et al., 1995). However, most R.C. found in experiments propagates forward, although the backward mode was also found recently (Hashimoto et al., 1996).