Influence of the Oblique Trimmed Impeller on Pressure Fluctuations in Centrifugal Pump at Low Flow Rate

At the low flow rate the recirculation occurred at the impeller outlet always induces the low frequency pressure fluctuation, which has severe influence on the safety of pumps. In order to investigate the influence of oblique trimmed impeller on the pressure fluctuation, two impellers with different exit geometry parameters were tested in the same volute. SST k-ω model was applied to the numerical simulation and the simulation results showed good agreement with the experimental results. Besides, some monitor points were arranged near the trailing edge of the impellers to record the pressure fluctuation. The internal flow field and pressure fluctuation characteristics under different flow rate conditions were also obtained. The simulation results showed that the recirculation zone near the original impeller outlet first occurred near the shroud, then moved to the hub and finally moved back to the shroud as the flow rate decrease. While the recirculation zone near the oblique trimmed impeller outlet always occurred near the hub at the low flow rate. The oblique trimmed impeller could decrease the pressure fluctuation level at the low flow rate and pressure fluctuation around the exit of the impeller at the low frequency is closely related to the recirculation phenomenon.