Based on the theory of flow control, a gap drainage impeller structure is proposed. Compared with the ordinary impellers, the updated gap drainage impeller can improve hydraulic performance and cavitation performance of centrifugal pump in certain aspects. Experimental results show that, with increase of flow, pressure pulsation and vibration in the volute and outlet region decrease first, and then increase when flow becomes larger. With a large flow, pressure pulsation and vibration of the gap drainage impeller centrifugal pump is obviously weaker than those of the ordinary centrifugal pumps. Numerical investigation shows that the gap drainage impeller has more uniform velocity distribution on the outlet of channel and weaker inner secondary transportation. These are the main reasons for making the pressure pulsation of the gap drainage impeller centrifugal pump weaker. As pressure pulsation is one of the main causes of vibration, the gap drainage impeller can improve operation stability of a low specific centrifugal pump. The main frequency for the ordinary centrifugal pump is the blade passing frequency (BPF). In contrast, the main frequency for the gap drainage impeller centrifugal pump is double BPF, which is the result of a unique gap structure. The main frequency of vibration in horizontal and vertical directions is double BPF. As to mutual correlation of pressure pulsation and vibration, the amplitude of BPF and double BPF is higher, confirming that pressure pulsation and vibration are closely related, and excited by the rotation of impeller.
