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The high-speed rotation of impellers leads to strong rotor-stator interaction, which mainly causes the pressure pulsation of centrifugal pumps. An impeller with a bionic sinusoidal tubercle trailing edge (STTE) can reduce the intensity of the rotor-stator interaction and thus reduce the pressure pulsation of the centrifugal pump. In this study three profiles of STTE were designed based on the pectoral fin structure of humpback whales of which the influence on the pressure pulsation of centrifugal pumps was studied via experiment and numerical simulation. Results show that a reasonable design of STTE can effectively eliminate the high-frequency pressure pulsation in the rotor-stator interaction region of the centrifugal pump. The use of STTE2 and STTE3 profiles affects the amplitude reduction of pressure pulsation at the blade passing frequency (fBPF). Compared with the impeller without the STTE profile, the amplitudes of pressure pulsation with STTE2 and STTE3 profiles are decreased by 47.10% and 44.20% at the pump discharge, while the decrease, at the volute throat are 30.36% and 25.97%, respectively. Detailed flow structures inside the pump show that the STTE profile can inhibit the vortex generation at the blade trailing edge, and the local high-intensity pressure pulsation can be reasonably avoided. This study helps improve the pressure pulsation characteristic of centrifugal pumps and their operation stability.

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The impeller, which is the main energy conversion component of a pump as turbine (PAT), is designed for pumping mode, and its internal flow characteristics are quite complicated even at the best efficiency point (BEP) of the turbine mode. This study aims to investigate the flow separation characteristics in a PAT impeller under the BEP condition by numerical method. The hydraulic performance and transient pressure characteristics of PAT predicted numerically were verified through experimentation. The surface friction lines and flow topological structure were applied to diagnose the flow separation at the surface of the blade. The relationship between flow topological structure and vortex in the impeller and static pressure at the blade were analyzed. Analysis results show that the backflow and open flow separation are observed significantly in the leading region and near the shroud of the trailing region of suction side. The passage vortex always appears near the spiral node. The saddle point and node correspond to the peak position of adverse pressure and the lowest position between two peak values of the static pressure of the blade, respectively. The inflow conditions of blade and shape of the trailing edge significantly influence the flow separations in the impeller.

High-speed centrifugal pumps are widely used in the aerospace and chemical industries. However, the large axial thrust of a rotor due to high rotating speeds exacerbates the device operation instability. Herein, the axial thrust characteristics of a high-speed centrifugal pump under variable speed conditions are analyzed via numerical simulations and experiments. Results show that at high rotating speeds, although the dynamic reaction of the impeller and axial force on the inducer blade only account for a small proportion of the axial thrust, they are the main sources of axial thrust instability. Moreover, axial thrust exhibits a linear relation with the axial force acting on the front and back surfaces of the impeller, and the values of these parameters are very close. However, huge errors are afforded when these two parameters are interchanged, and many axial thrust estimation models ignore this. Therefore, considering the influence of the impeller dynamic reaction and the axial force of the inducer blade on axial thrust, this study proposes an estimation theory for predicting axial thrust. Comparison of the prediction results of the estimation theory and the numerical simulation results reveals that the maximum and minimum relative errors of these two parameters are 11.1% and 2.6%, respectively, under different rotational speeds, thereby suggesting that the prediction results of the estimation theory are sufficiently accurate. The estimation theory can greatly reduce the calculation cost, shorten the design cycle of the centrifugal pump, and provide certain reference for engineering practice.