Experimental Study on Transient Startup Characteristics of a Super Low Specific Speed Centrifugal Pump

Abstract

In this paper, the transient behavior of a super low speci c speed centrifugal pump, with the speci c speed of 25, during startup period under shut-o 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 di erent accelerated speeds under shut-o 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 uctuation 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-o 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 speci c speed centrifugal pump will accelerate the cavitation. The results provide references for further study of the transient characteristics of the super low speci c speed centrifugal pump.

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