Abstract: A three-dimensional unsteady numerical investigation is carried out in a screw centrifugal pump to study axial force, impeller radial force and pressure fluctuation rule of different instantaneous and conditions on monitoring points based on Reynolds Navier-Stokes in multiple reference frames and the RNG turbulence model. The results obtained show that the error is less than 2.5% to predict efficiency and head using unsteady and unsteady numerical model. The pressure fluctuations on the monitoring points have obvious periodic in the case, and the pressure of P3 has a severe fluctuations, and appear two times the pressure fluctuation. The pressure fluctuations of P2 near volute tongue is severe with the flow rate from low to high, and the pressure fluctuations range increase four times when flow rate increase a time. The monitoring point pressure fluctuation on the suction surface and pressure surface of blade inlet have obvious periodic, and pressure fluctuations on the suction surface are more than pressure surface. With the flow rate increasing, the pressure fluctuations increase obviously, and with flow rate changing, the pressure fluctuations are greater influence on the surfaces of blade inlet than blade outlet. The direction of the radial force is periodic changes, meanwhile as flow rate from high to low, the direction moves near to the volute tongue gradually. With the reduction of flow rate, the fluctuations range of radial force increase, but there is large radical force in design condition. Axial force has fluctuation but its range is very small, and with the value of head decreasing, the axial forces reduce in a nonlinear.

Key words: Numerical analysis, Pressure fluctuation, Screw-type centrifugal pump, Transient regime