SUPPRESSION OF CAVITATION INSTABILITIES IN AN INDUCER BY J-GROOVE

A BSTRACT The suppression of cavitation instabilities was attempted through the control of tip leakage vortex cavitation. The control was made by using shallow grooves, called J-groove, on the casing wal~. With Jgroove, the onset rea.ions of the rotating cavitation and the asymrneinc cavitation could be dirninished. However, a cavitation surge appeared at higher cavitation numbers. From the observation of cavitation, it was found that the cavitation surge occurred when the tip leakage vortex cavitation started to interact with the leading edge of the next blade. This type of cavitation surge could be avoided by extendin.a the leading edge of J-groove upstream. However, in this case, another type of cavitation surge occurred at much lower cavitation numbers, which was caused by the cavitation between the blade surface and the tip leakage vortex cavitation. These results highlight the importance of the tip leakage vortex cavitation for cavitation instabilities.