2019 Volume 52 Issue 9 Pages 743-750
In this paper, the transient behavior of a super low specific speed centrifugal pump, with the specific speed of 25, during startup period under shut-off condition and rapid depressurization process at the pump inlet is experimentally studied. The pump performance and vibration are tested under given transient operating conditions. The experimental results show that the motor speed linearly increases when the pump started up with different accelerated speeds under shut-off condition, and reaches its highest value at the end of the startup. Meanwhile, an obvious impact head at the end of the acceleration process is found, and then declines as the startup becomes steady. The main fluctuation frequencies of the vibration acceleration in the X, Y, and Z directions at the outlet are shaft frequency or integer times of shaft frequency during the startup period with shut-off condition. The vibration acceleration amplitude had the largest component in the X direction, while the smallest component was in the Z direction. As the acceleration of startup increased, the vibration acceleration amplitude also increased with the main frequency. Compared with the instantaneous depressurization process and the stable non-cavitation condition, there is a broadband vibration ranging from 4000 Hz to 6000 Hz. The abrupt reduction of the inlet pressure of the super low specific speed centrifugal pump will accelerate the cavitation. The results provide references for further study of the transient characteristics of the super low specific speed centrifugal pump.