At off-design points, diffuser pumps often experience significantly restricted operating ranges due to the induction of unstable phenomena, such as diffuser rotating stall (DRS), caused by unsteady flow effects. This presents a major issue in various industries. This study aims to suppress the backflow from the diffuser vane outlet to the inlet, which contributes to the development of DRS. A CFD analysis was conducted on a modified diffuser featuring sweep-shaped holes. These holes extend from the leading edge of the diffuser vanes, pass through the vane interior, and exit via the vane's suction surface. The objective of this analysis was to investigate the effectiveness of this design in suppressing DRS. As a result, the number of backflows from the diffuser channel outlet was reduced at the 50% flow rate point. Furthermore, efficiency at the design point improved by a maximum of approximately 1.5%.
YANAGIHARA et al. (2025) studied this question.