Effects of Alternate Uneven Blade Length on Unsteady Cavitation in 4-Bladed Inducers. 1st Report. In Case of Weak Uneven Blade Length.

Abstract

With an aim of suppressing the rotating cavitation by cutting back the leading edge alternately, 4-bladed inducers with uneven blade length were designed. Unsteady cavitations were observed through inlet pressure measurements and high-speed video pictures, covering a wide range of flow rate and cavitation number. It was found that, with the alternate cutting back of leading edge, the range of alternate blade cavitation was extended, and the region of rotating cavitation was diminished. However, the cavitation surge occurred instead of the rotating cavitation. In addition, two types of alternate blade cavitation were found as predicted theoretically. One of them is with longer cavities on longer blades, and the other is with longer cavities on shorter blades. Hysteresis in the alternate blade cavitation pattern was observed depending on the increase or decrease of cavitation number at low flow rate.