Suppression of Cavitation Instabilities in an Inducer by J-Groove (Control by the Change of Axial Location)

Abstract

The results of the control of tip leakage vortex cavitation, and cavitation instabilities, are discussed. The control was made by adjusting the axial location of the leading and trailing edges of shallow grooves, called J-grooves, on the casing wall. If the leading edge of the groove is too close to the leading edge to the impeller blade, the tip leakage vortex is trapped by the groove leading edge and the tip leakage vortex cavitation approaches the leading edge of the next blade. A premature severe cavitation surge occurs when the tip leakage vortex cavitation starts to interact with the leading edge. This type of cavitation surge can be avoided by extending the groove leading edge upstream. However, in this case another type of cavitation surge occurs at much lower cavitation number caused by the cavitation between the blade surface and the tip leakage vortex cavitation. Thus, the importance of the tip leakage vortex cavitation for cavitation instability are shown by a series of experiments using J-grooves.