Slanted axial-flow pump devices are widely applied in urban water supply, irrigation and drainage engineering fields. The second law of thermodynamics is applied to investigate the flow loss characteristics of the 30° slanted axial-flow pump model according to the flow loss analysis method of entropy production theory, so that the hydraulic loss characteristics can be revealed in internal flow process of the slanted axial-flow pump. The three-dimensional numerical simulation of the whole flow conduit in slanted axial-flow pump was conducted and the entropy production increased in the flow process was calculated. The location and distribution characteristics of the flow loss of the pump were qualitatively analysed. The results show that the entropy production in impeller is the highest among the pump components. With the increase of flow rate, the proportion of the entropy production in impeller in total value of the pump device increases continuously. The wall entropy production of impeller, guide vane and outlet conduit are lower than the mainstream entropy production, and the mainstream entropy production occupies the dominant position. As the flow rate grows, the proportion of turbulent dissipation entropy production decreases, and the proportion of wall dissipation entropy production increases. At 0.8 Q bep , the proportion of turbulent dissipation entropy production is close to 74%, which is about 2.8 times that of wall entropy production. Under 1.2 Q bep condition, the proportion of turbulent dissipation entropy production is just 5.5% higher than that of wall dissipation entropy production.

The outlet conduit is an important construction connecting the outlet of the pump guide vane and the outlet pool; in order to study the hydraulic performance of the straight outlet conduit of the axial-flow pump device, this paper adopts the method of numerical simulation and analyzes the influence of the division pier on the pressure and velocity distribution inside and near the wall of the straight outlet conduit based on three design schemes. Four pressure pulsation measuring points were arranged in the straight outlet conduit, and the low-frequency pulsation characteristic information inside the straight outlet conduit with and without the division pier was extracted by wavelet packet reconstruction. The results show that the addition of a division pier has an effect on the hydraulic loss, near-wall pressure and velocity distribution in the straight outlet conduit. A small high-pressure zone is formed near the wall at the starting position of the division pier, and a large high-speed zone is formed on the left side at the starting position of the division pier. The length of the division pier has no significant effect on the flow distribution of the straight outlet conduit and the pressure and velocity distribution near the wall. Under different working conditions, each monitoring point has the maximum energy in the sub-band (0~31.25 Hz). With the increase of the flow rate, the total pressure energy of the straight outlet conduit decreases gradually. Under each condition, the difference of the energy proportion of the horizontal monitoring points of the straight outlet conduit is small, and the difference of the energy proportion of the two monitoring points at the top and bottom of the outlet channel is relatively large. The energy of the two monitoring points in the straight outlet conduit with a division pier is smaller than that of the two monitoring points in the straight outlet conduit without a division pier. There are differences in the main frequency and the power spectrum corresponding to the main frequency of the monitoring points in the straight outlet conduit, and the reasonable setting of the division pier is conducive to reducing the pressure pulsation of the flow in the straight outlet conduit and is beneficial to the safe and stable operation of the pump device.

The complex flow inside the axial-flow pump device will cause the problem of hydraulic noise; in order to explore the influence of the law of rotation speed on the internal flow characteristics and hydraulic noise of the axial-flow pump conduit, a combination of Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) was used to numerically solve the flow field and internal sound field in the pump device. The results showed that the flow in the elbow inlet conduit was smooth at different rotation speeds, and there was no obvious unstable flow. The higher the rotation speed, the more disordered the flow pattern in the left half of the elbow, which intensifies the unstable flow in the straight outlet conduit. The impeller is the main sound source of the internal hydrodynamic noise of the vertical axial-flow pump device. When the sound source propagates upstream and downstream along the conduit, the Total Sound Source Intensity (TSSI) gradually decays with the increase of distance; the greater the rotation speed is, the faster the Total Sound Source Intensity (TSSI) decays. When the rotation speed was increased from 1450 r/min to 2200 r/min, the TSSI in the straight outlet conduit was attenuated by 8.9 dB, 13.9 dB, and 16.0 dB respectively, and the TSSI in the elbow inlet conduit was attenuated by 11.0 dB, 13.5 dB, and 25.9 dB respectively. The vortex structure in the conduit induces flow noise and delays the attenuation of TSSI in the propagation process; with the increase of rotation speed, this delay will be more obvious.

The forebay of a pumping station is an important building connecting the diversion channel and the intake pool. Based on the physical model test and research method of computational fluid dynamics (CFD) based on the improved fluid volume model, the flow field in a forebay of a multi-unit pumping station is analyzed in combination with the engineering practice of the Exi River flood discharge station in the Anhui Province, China. Aiming at the technical problems of a large-scale swing water area in the forebay internal flow field of a lateral intake pumping station, the technical problems are discussed. Different rectification measures are selected to adjust the flow pattern in the forebay of a pumping station. The internal rectification flow pattern in the forebay under different plans, the uniformity of flow velocity distribution in the measurement section, and the reduction rate of the vortex area are studied and compared, and the optimal plan is given. The results show that the flow pattern of the 7.5 m and 15 m solutions of the lengthened inflow wall is still poor, and the ability to eliminate vortices is not strong or even counterproductive. The combination plan of a rectifier sill and a rectifier pier has a better effect and can eliminate more than 90% of the vortex, but the uniformity of flow speed has not been significantly improved at the inlet of the pumping station; the combination plan of a rectifier sill and a diversion wall opening has the best effect; the reduction rate of the vortex area is more than 85%, and the velocity uniformity of three measuring sections is better than that of the original plan. The uniformity of flow rate near the pumping station is increased by 4% and that far away from the pumping station is increased by 13%. The combination plan of a rectifier sill and diversion wall with openings is recommended.

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