Abstract：Abstract: The unsteady flow in centrifugal pumps induces a pulsation in fluid pressure inside the volute channel and imposes a radial force on the volute wall too. Thus effect of the gap between the volute tongue and impeller outlet on them was tackled by means of a nonoverload submersible sewage pump with extremely thickenedblades. Three pump models with different base circle diameters, such as 390, 435 and 460 mm were designed. The unsteady flow fields in those models were obtained numerically based on the standard k-ε turbulence model and SIMPLE algorithm. The characteristics of pressure pulsation on the tongue and the radial force on the wall against gap were obtained. The results showed that the pressure pulsation and the radial force presented an obvious periodicity due to the rotorstator interaction. The dominant frequency of pressure pulsation at the monitor points in the volute was the blade passing frequency. At the same flow rate, the intensity and amplitude of pressure pulsation at the dominant frequency were increased with decreasing gap.The timeaveraged radial force imposed on the wall was decreased and then increased with increasing flow rate.Compared with the original pump model, the averaged radial force in the new models was increased regardless of gap at the same flow rate.
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