低比速度斜流ディフューザポンプで発生する旋回失速挙動とその抑制

概要

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In the present paper, the design guide line of mixed-flow pump with a low specific speed is discussed. Tested pump has a positive slope of head-flow characteristics at low flow rate due to a rotating stall in the vaned diffuser. In the authors previous studies, it is confirmed that the flow instability is firstly formed in the vaned diffuser hub-side and it causes to diffuser rotating stall, based on the results obtained by both dynamic Particle Image Velocimetry (PIV) measurement and numerical simulation of Computational Fluid Dynamics (CFD). Considering those results, different vaned diffusers were designed to suppress the backflow at further low flow rates. Those pumps are simulated and tested. As a result, it is clarified that the leading edge of the vaned diffuser had better been approached toward the impeller outlet and the vane loading should be after-loaded in order to improve characteristic instability.