Experimental Study on a Prototype Centrifugal Pump with Open Impeller During Stopping Period

The transient hydraulic performance of vane pumps during abrupt stopping period has drawn more and more attentions in recent years. In order to reveal the transient characteristics of a low-specific-speed prototype centrifugal pump with an open impeller during stopping period, a transient test bed is built to obtain the variation characteristics of performance parameters, such as rotating speed, static pressures at pump inlet and outlet, pump head, flow rate, shaft torque, and shaft power. The experiments are accomplished on the condition of different valve openings. The experimental results show that besides the shut-off condition, the time for the open impeller to stop rotating is shorter and shorter with the increase of the stable flow rate before stopping. Moreover, the rotating speed curves become more steep. On the condition of eight valve openings, the rotating speed curves basically meet the cubic varieties. An important characteristic of flow rate curves is to show the three segmentation feature, that is to say, the early, middle, and late stages appear in these flow rate curves. It is also seen that on the beginning of the stopping (about before 1 s), the variation of flow rate is relatively stable, and greatly delayed to the decrease histories of rotating speed. With the increase of the stable flow rate before stopping, the time for the flow rate to achieve relatively stable displays a slightly decreasing tendency. Meanwhile, the time for the flow to thoroughly stop becomes more and more, this characteristic are completely opposite to that of rotating speed curves. The variations of the static pressures at pump inlet are very violent during whole stopping periods, and gradually become relatively stable at about 6 s. At about 4 : 5 s, the static pressure at pump outlet and the pump head decrease to the corresponding stable values. The variation tendencies of the shaft torque and shaft power is basically consistent, both of them rapidly decline with the rapid decrease of the rotating speed.