ロケットインデューサに発生する超同期旋回キャビテーションの振動特性に関する数値解析

抄録

The phenomenon of super-synchronous rotating cavitation (super-S RC) has been observed in liquid rocket inducers. This phenomenon is known to induce axial oscillations of about 1.2 times the inducer rotation speed. Tsujimoto et al. have investigated in detail the region where super-S RC occurs when the flow rate and cavitation number are varied, but the mechanism has not been fully elucidated. In this study, the oscillation characteristics of the cavity in the inducer were evaluated by numerical analysis at several rotation speeds using general-purpose software. The results showed that the cavity frequencies of equal length cavitation (EC) and super-S RC were continuously monotonically decreasing, while the cavity frequencies of synchronous rotating cavitation (sync RC) and cavitation surge (CS) were not monotonically decreasing. Furthermore, the maximum cavity length was found to be independent of the rotation speed. A comparison of the Strouhal number using the cavity length showed that the Strouhal number was almost equal not only for EC and super-S RC, where the cavity frequency was continuously monotonic, but also for sync RC, which deviated from the monotonic decrease. On the other hand, the Strouhal number in CS was discontinuously high. This indicates that the super-S RC and sync RC, which are locally unstable, and the EC, which is stable, share the same cavitation characteristics, while the CS, which is system unstable, has distinctly different characteristics.