Effects of Leading Edge Sweep on Unsteady Cavitation in Inducers. 2nd Report. Problems of Forward and Backward Sweep.

Abstract

With an aim to clarify the effects of leading edge sweep on unsteady cavitation, four inducers with backward/forward leading edge sweep were examined. It was found that the cavity length at the tip is made shorten by both backward/forward leading edge sweep, and cavitation performances are also improved. In addition, the shape of leading edge affects the development of the blade cavitation at inner radial location. With forward sweep, the blade cavitation at the mid-span occurs considerably, which begins at the leading edge. On the contrary, with backward sweep, no blade cavitation develops at the mid-span. For unsteady cavitation, backward leading edge sweep is very effective in suppressing the unsteady cavitation, and an inducer with strong backward sweep could totally suppress the rotating cavitation, although the inlet backflow occurs more easily. On the other hand, an inducer with strong forward leading edge sweep suffers from various types of unsteady cavitation including backward rotating cavitation, although the head breakdown occurs at significantly smaller cavitation number.