In order to study the changes in performance and vibration characteristics for different structures in a series-parallel centrifugal pump, the original volute of a series-parallel centrifugal pump is replaced with a new structure-radial diffuser plus annular ring. The hydraulic design of the two structures is conducted by making use of existing hydraulic models and velocity constants method. An experimental stand is built according to relevant standards, then the performance and vibration characteristics of the pumps with two structures are measured on the stand, respectively. The vibration is monitored in the pump feet and analyzed in 1/3 octave band of vibration acceleration. The results show that the original volute configuration can achieve a higher pump efficiency but is subject to a high vibration level than the new structure. In particular, the noise level of the pump with the new structure is 3dB-4dB lower than the pump with the original volute structure. Unfortunately, the vibration characteristics at various monitoring points don′t show any regular patterns at each octave, and the noise changes from one monitoring point to another. As a result, when monitored parameters are assessed, all monitoring points should be taken into consideration in a comprehensive manner.
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