Experimental study on the flow in mixed pump impeller by PIV

A mixed-flow pump with unshrouded impeller was manufactured, and the flow in the impeller at design and off-design flow rates was measured by particle image velocimetry (PIV). The distribution of time-averaged relative velocity showed the velocity near blade pressure surface at design flow rate decreased and then increased from inlet to outlet of the impeller, and that near blade suction surface increased and then decreased. At the impeller outlet, the relative velocity near blade pressure surface varied a little along the span direction; near the suction surface decreased from hub to casing, and the minimal velocity appeared near the casing and suction surface. Back-flow was found near casing and mid-span sections at partial flow rate. The velocity distribution in different impeller passages was similar.