In recent years, vibration sources

In recent years, vibration sources nurtured in inner flows of the impeller pump have gained much attention, and it has been verified in some cases that static pressure fluctuations and pump vibration share typical frequencies .Most of these frequencies are harmonics of shaft frequency or blade passing frequency.The axial-flow pump is featured by unsteady flows between impeller blades and stator vanes. Although numerous efforts have been dedicated to the impeller–stator interaction in the axial-flow pump, a clear explanation of this subject is still sorely necessitated. This study is anticipated to provide a further insight into axial-flow pump performance, as well as inner flow characteristics in the pump with different combinations of impeller blades and stator vanes.Several studies confirmed the connection between flow characteristics and operation performance of the pump, but no robust explanation has been furnished so far . Since some factors such as mechanical loss and leakage loss were not taken into account in numerical simulation, the operation performance of the pump predicted numerically inevitably incorporated errors. Under such a circumstance, a performance test was carried out on the test platform in Shanghai Kaiquan Pump Group Co., Ltd. Through adjustments and regulation sperformed on the experimental system, the maximum uncertainties for measurements of pump head and pump efficiency were less than 1% and 1.8%， respectively. Both pump head and pump efficiency were measured for the three pumps with different vane numbers and the results are plotted in picture.Vane number affects both energy transformation capability and inner flow characteristics of the axial-flow pump. Pump head curves associated with the three vane number cases are in modest agreement, while the 7-vane case proves to be the most preferable one in terms of pump efficiency. The 9-vane case has the lowest overall pump efficiency. Nevertheless, large vane number facilitates the rise in velocity distribution uniformity at both impeller outlet and stator outlet. Variation in vane number accounts for an insignificant change in terms of pump vibration. Apart from the circumferentially even vibration monitored on the motor base, high vibration level arises at two local positions on the supporting plate: one is near the outlet bend of the pump and the other is adjacent to the inflow pipe. Both structural and hydraulic factors are pivotal in this context. At nominal flow rate, mini-mum pump vibration level is manifested. Frequency spectra of pressure fluctuations between the impeller and the stator are overwhelmingly dominated by blade passing frequency and its harmonics, as is shared by the three cases. Compared with the other two cases, the 7-vane case has relatively low characteristic pressure fluctuation amplitudes.As flow rate increases from 0.8Q to 1.0Q, all characteristic pressure fluctuation amplitudes decline with the 5-vane case, while the 9-vane case is featured by active low-order harmonics together with decayed high-frequency components.