Pressure Fluctuation Characteristics Analysis of Centrifugal Pump as Turbine in Its Start-Up Process

In order to study pressure fluctuation characteristics of a centrifugal pump as turbine (PAT) in its start-up process, Fluent was used to do numerical simulation of the PAT start-up process. Time and frequency domain analyses were performed on the data acquired at different positions and different heads. The results show that a large number of low-pressure areas and strong vortexes are formed within the impeller at the initial time of start-up. With the increase in rotating speed, the vortexes rapidly decrease and are concentrated on the blade non-working face. The pressure fluctuation amplitude is the maximum at the start-up initial instant; with increase in rotating speed, it reduces rapidly at the volute spiral part. The pressure fluctuation number within one impeller rotation cycle is consistent with blade number, and the dominant frequency of pressure fluctuation is 6 times the impeller rotational frequency. The dominant frequency amplitude of radial pressure fluctuation increases with decrease in radial size in the volute. The pressure fluctuation in the impeller is much more intensive than that in the volute, and its maximum dominant frequency amplitude occurs in the middle of the impeller towards the inner edge. With the increase in head, the number of pressure fluctuation and the amplitude of dominant frequency increase at the same time during the start-up process.