Pressure fluctuation characteristics of centrifugal pump at low flow rate

Abstract

The current investigation is aimed to simulate the unsteady internal flows in a centrifugal pump impeller with seven twisted blades by using a three-dimensional Navier-Stokes equations with Scale-adaptive simulation (SAS) turbulence model. A detailed analysis of the results at design flow rate Q0 and low flow rate 0.5Q0 and 0.3Q0, is presented. Unsteady flow analyses in centrifugal pump are focused mainly on the volute. The calculation results of pump head and efficiency at different flow rate conditions is in good agreement with the experimental data. Nine monitor points are positioned in the volute. The frequency of pressure fluctuations on all monitor points are analyzed and discussed. Under different flow rate conditions, the dominant frequency of pressure fluctuation in volute are the blade pass frequency and its integer multiples, the blade pass frequency always played the dominant role, and the largest pressure fluctuation maximum amplitude occurs near the volute tongue zone. With the flow rate decrease, the intensity of pressure fluctuation gets stronger, especially in spiral zone is the most obvious and the amplitude value of pressure fluctuation is the most dramatically increased. The maximum amplitude of pressure fluctuation in spiral zone is about 2∼3 times of design flow rate. Moreover, the streamline distribution in pump flow passage at flow rate Q0, 0.5Q0 and 0.3Q0 is analyzed. The results demonstrate that with the flow rate decrease, the vortex in the impeller flow passage is generating, developing and even blocking the whole impeller flow passage, which is disturbs the internal flow field and induces the strong pressure fluctuations in volute spiral zone. This research provided a reference for expanding the operation range of centrifugal pump and optimization design of volute in centrifugal pump.