In order to study steady and transient characteristics of fluid flow in centrifugal multistage pumps, the unsteady flow field in two stages of a multistage centrifugal pump made of stainless steel was simulated under design flow condition by making use of ANSYS CFX and the standard k-ε turbulence model. The performance curves predicted are in good agreement with the experimental data, validating the accuracy of the flow models and numerical methods. Additionally, four monitoring points are specified on the pressure and suction sides in a flow passage of the impeller, respectively; meanwhile other six monitoring points are positioned in various locations in a flow passage of the diffuser and guide vane. The pressure pulsation characteristics are analysed in time and frequency domains at these points. The results show that the rotor-stator interaction between impeller and guide vane is the cause for the static pressure fluctuation, and the average fluctuation of static pressure increases gradually from the inlet to the outlet of impeller. The shape of integrally formed stamping impeller can affect the pressure pulsation in the diffuser, and the pressure pulsation in one period is similar in another. The influence of rotor-stator interaction is dominated in the first guide vane; as a result, the pressure fluctuation is in 3 times blade passing frequency in the middle and at the outlet of guide vane, but is in 1 time blade passing frequency only at the other locations. The pressure pulsation in the diffuser is in a frequency as low as blade passing frequency.
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