Effect of diffuser vane slit on rotating stall behavior and pump performance in a centrifugal pump

In the previous study of a centrifugal pump with a vaned diffuser, it was confirmed that the flowrate at the onset of rotating stall was shifted to the lower flowrate by slitting the diffuser vanes. As the CFD result, it was found that the jet flow from pressure-side to suction-side impinges backflow near the suction surface and it suppresses to expand toward the diffuser inlet. However, it is difficult to say that the optimized shape and slitting position have been sufficiently studied. Therefore, in this study, we investigated the effect of slitting on the pump performance and internal flow by adding another slitting to the diffuser vane with slit. In order to clarify the suppression effect of the jet flow in detail, the effect of adding slits at two locations was verified. The pump performance was compared for these diffusers. The effect of slitting on the diffuser vanes on the occurrence of rotating stall was clarified by the experimental and numerical study.