Yoshinobu Tsujimoto

Theoretical Analysis of Cavitation in Inducers With Unequal Blades With Alternate Leading Edge Cutback: Part I—Analytical Methods and the Results for Smaller Amount of Cutback

With the idea of reducing the region of rotating cavitation by cutting back the leading edge of blade alternately and enhancing the stability of alternate blade cavitation, an analysis of steady cavitation and its stability were made for unequal blade cascade. The cavities on longer uncut blades are generally longer but they become shorter in a certain range of inlet cavitation number. This peculiar behavior is explained by an interaction effect of a local flow near cavity closure with the leading edge of the opposing blades. The region with stable cavities can be extended and the onset region of rotating cavitation can be diminished by cutting back the leading edge of blade alternately

1016 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.

Theoretical analysis of cavitation in inducers with uneven length blades (2nd report, effects of the amount of cutting back)

The present report describes about the effects of the amount of the alternate cutting back of the leading edges on the steady cavitation, its stability and the onset region of rotating cavitation. It was found that, by increasing the amount of cutting back, we can increase the range of cavitation number with stable cavitation and diminish the onset region of rotating cavitation.