Explore the vast range of titles available.

According to the relevant literature of pumps and pumping stations and the expression and conversion method of pump efficiency and pump cavitation proposed by the author, through further careful mathematical deduction, the expression of pump and pump device characteristics is proposed. The proposed expressions for centrifugal pumps (and volute type mixed flow pumps) and axial flow pumps (and guide vane type mixed flow pumps) are applicable to both pumps and pump units; it is applicable not only to models, but also to similar prototype pumps and prototype pumping units of any diameter and parameters. The research and realization of performance expression of pumps and pump devices have great theoretical significance and practical application value for improving the design level of pumps and pumping stations and for accurately predicting the characteristics of pumps and pumping stations.

The energy loss of the vertical axial flow pump device increases due to the unstable internal flow, which reduces the efficiency of the pump device and increases its energy consumption of the pump device. The research results of the flow loss characteristics of the total internal conduit are still unclear. Therefore, to show the internal energy loss mechanism of the axial flow pump, this paper used the entropy production method to calculate the energy loss of the total conduit of the pump device to clarify the internal energy loss mechanism of the pump device. The results show that the energy loss of the impeller is the largest under various flow conditions, accounting for more than 40% of the total energy loss of the pump device. The variation trend of the volume average entropy production and the energy loss is similar under various flow coefficients (KQ). The volume average entropy production rate (EPR) and the energy loss decrease first and then increase with the increase of flow, the minimum volume average entropy production is 378,000 W/m3 at KQ = 0.52, and the area average EPR of the impeller increases gradually with the increase of flow. Under various flow coefficient KQ, the energy loss of campaniform inlet conduit is the smallest, accounting for less than 1% of the total energy loss. Its maximum value is 63.58 W. The energy loss of the guide vane and elbow increases with the increase of flow coefficient KQ, and the maximum ratio of energy loss to the total energy loss of the pump device is 29% and 21%, respectively, at small flow condition KQ = 0.38. The energy loss of straight outlet conduit reduces first and then increases with the increase of flow coefficient KQ. When flow coefficient KQ = 0.62, it accounts for 27% of the total energy loss of the pump device, but its area average entropy production rate (EPR) and volume average entropy production rate (EPR) are small. The main entropy production loss in the pump device is dominated by entropy production by turbulent dissipation (EPTD), and the proportion of entropy production by direct dissipation (EPDD) is the smallest.

【Objective】 Pumping station is an important component in hydraulic projects and its performance and efficiency are affected by many factors. This paper aims to investigate the performance of the box-type bidirectional vertical pump, as well as the influence of the guide vane body on its efficiency. 【Method】 The box-type bidirectional vertical flow pump system at the Jiangsu Riverside Hub Pumping Station was used in this study; physical model was used to test its energy performance, cavitation performance and flyaway performance. The flow characteristics inside the pump were analyzed using numerical simulation. 【Result】 ①The efficiency of the box-type bidirectional vertical axial flow pump is 57.24%. ②When the vane placement angle is -6 degrees and water lift height is 1.75m, the efficiency of the pump is 60.77%. ③Within the range of operating water lift height, 1.75 3.95 m, the critical cavitation allowance of the axial flow pump does not exceed 8.0 m, meeting the requirement on minimum submergence depth. 【Conclusion】 Comparison of difference guide vane bodies showed that efficiency of the pump with a diffusion guide vane is higher than that with a straight guide vane. Under all operating conditions we tested, the front streamline in the flow field in box-type bi-directional intake channel is smooth; at the blind end of the bi-directional intake channel, the flow velocity is very small. On average, the flow distribution in the outlet side is relatively uniform, and there are no undesirable flow patterns in it.

Safety barriers are commonly installed at the inlet passage entrances of large and medium-sized low-lift pump stations to intercept floating debris and ensure the safety of humans and animals. To clarify the variation of internal pressure pulsations and hydraulic noise of axial-flow pumps when the safety barrier is blocked, numerical simulation of a vertical axial-flow pump device with a safety barrier at 0.3 blockage ratio under different flow conditions was conducted using the VLES k–ω model. Fast Fourier transform was applied to transform the time-domain signals of both pressure pulsations and hydraulic noise. The study explores the correlation between pressure pulsations and hydraulic noise using coherence theory. The results show that, at all flow conditions, the amplitude of pressure pulsations and hydraulic noise increases from hub to rim at monitoring points at impeller inlet, outlet and guide vane outlet. The pressure pulsation time-domain amplitude range increases from (−0.008 to 0.007) to (−0.195 to 0.131), while frequency-domain amplitude range increases from 0.002–0.013 to 0.003–0.092. The average sound pressure level of hydraulic noise increases from 92.98–106.49 to 107.64–114.41 dB. The main frequencies of pressure pulsations and hydraulic noise were concentrated around fBPF, with secondary frequencies observed at 8fn and fn. Strong correlations (γ2 ≥ 0.9) between pressure pulsations and hydraulic noise mainly occurred in the vicinity of fBPF and fn.

The rotation speed of water at the inlet of the low hump outlet conduit has a great effect on its hydraulic performance. Therefore, the influence of different inlet water rotation speeds on hydraulic loss and flow pattern of low hump outlet conduit is studied in this paper. By solving RANS equations and the RNG k-ε turbulence model, the hydraulic loss and 3D flow field of the low hump outlet conduit were calculated under different inlet water rotation speeds. To verify the numerical results, the model tests of low hump outlet conduit with different guide vanes were conducted. The results show that along with the growth of inlet water rotation speed, the hydraulic loss of outlet conduit will firstly decrease by degrees and then increase dramatically, the vortex location moves from the whole bottom of the descent segment to the right bottom of descent segment and the vortex area becomes smaller, the flow pattern of the whole conduit is improved obviously. The hydraulic loss and flow field of numerical simulation are consistent with those of the model test. Because of its great influence on hydraulic performance, inlet water rotation speed must be taken into consideration in the hydraulic optimization design of guide vane and low hump outlet conduit.

【Objective】 Bidirectional shaft tubular pump is a device commonly used in hydraulic projects. The aim of this paper is to study the impact of guide vane numbers on the force imposed to the pump when it is under different working conditions. 【Method】 The investigation was based on computational fluid dynamics (CFD) and experiments conducted in a real engineering project. Water flow in the pump was turbulent and described by the RNG k-ε turbulence model. The experimental data was used to calibrate the model, and the validated model was then used to analyze the impact of guide vane numbers on the pump under different working conditions. 【Result】 Under back and forth operation condition, the average axial force imposed to the pump by different guide vane numbers was comparable. Making the ratio of guide vane numbers to blade numbers an integer increased the peak axial force pulsation significantly, risking pump operation. The radial force imposed to the impeller was minimal and can be neglected in design. It was also found that setting the number of guide vanes even can reduce the radial force imposed to the pump by the guide vane. 【Conclusion】 The number of guide vanes and the number of blades combined to affect the force imposed to the pump. Our results indicated that design should avoid the ratio of the guide vane numbers to the blade numbers being an integer.

The unstable flow of a shaft tubular pump device (STPD) leads to energy loss, thereby reducing its efficiency. The aim of this study is to investigate the distribution pattern of energy loss in STPDs. This paper reveals that the two components with the highest proportion of energy loss are the impeller and the outlet passage. Furthermore, turbulent entropy production is the primary cause of energy loss. Due to the wall effect, the energy loss in the impeller mainly occurs near the hub and shroud. Additionally, the presence of a tip leakage vortex near the shroud further contributes to the energy loss in the region near the shroud. This results in the energy loss proportion exceeding 40% in the region with a volume fraction of 14% near the shroud. In the outlet passage, the energy loss mainly occurs in the front region, with a volume fraction of 30%, and the energy loss in this part accounts for more than 65%. Finally, this study reveals the locations of the vortex in the STPD under different flow-rate conditions, and when the distribution of energy loss is visualized, it is found that the energy loss occurs high in the vortex regions.

The influence of inflow angle on the stall characteristics of a vertical axial flow pump is investigated numerically by solving the unsteady Reynolds-averaged Navier–Stokes equations. The study predicts both performance parameters and internal flow structures under varying inflow conditions. It is found that as the deflection angle decreases, both the critical and deep stall points shift toward higher flow rates. For the −30° scheme, the design efficiency and design head decrease by 16.27% and increase by 19.59%, respectively, compared to the 0° scheme. As stall develops, an axisymmetric blockage region forms at the impeller inlet, which reduces axial velocity and increases the impeller’s angle of attack. Under design conditions, a smaller deflection angle exacerbates boundary layer separation near the blade leading edge, thereby weakening the local work capacity and intensifying turbulent dissipation. Furthermore, although a reduced deflection angle promotes an earlier onset of stall, it also leads to a decrease in the instability intensity of the stall flow field. These results reveal a critical trade-off: while a smaller deflection angle promotes an earlier stall onset, it effectively mitigates the intensity of stall instability, providing crucial guidance for optimizing the hydraulic design and operational stability of vertical axial flow pumps.

This study investigates the leakage vortex influence on pressure pulsation characteristics within a vertical axial flow pump. Three impeller configurations with blade root clearance (δ) of 2.7–8.0 mm were designed to analyze geometric effects on internal flow dynamics. Unsteady RANS simulations predicted flow structures under multiple operating conditions (0.8–1.2Qdes). Fast Fourier Transform (FFT) extracted frequency–domain and time–frequency characteristics of pressure pulsations in critical flow regions. Key results reveal: (1) δ enlargement expands low-pressure zones within blade channels due to enhanced leakage vortices; (2) leading-edge pulsation shows 8.2–11.7% reduction in peak-to-peak amplitude and fundamental frequency magnitude with increasing δ; (3) trailing-edge response exhibits non-monotonic behavior, with maximum amplitude at δ = 5.0 mm (42.2% increase at design flow). These findings demonstrate that blade root clearance optimization requires condition-dependent thresholds to balance leakage management and pulsation control.

【Objective】 The purpose of this paper is to improve the hydraulic performance of the pump device in the reconstructed project of Siyang Second Station and clarify its hydraulic performance. 【Method】 Taking the vertical axial-flow pump device in Siyang Second Station as an example, the hydraulic performance of its original pump device was analyzed numerically, from which we optimized its inlet and outlet conduits. With D representing the nominal impeller diameter, the dimensions of the original elbow inlet conduit was: height, 1.707D, length, 3.895D, and inlet area, 4.984D2; the dimensions of the original siphon outlet conduit was: inlet diameter, 1.09D, length, 6.14D, outlet area, 3.934D2. The energy performance parameters of the pump device were obtained by physical model test. 【Result】 The optimization of the square rounded tapering geometric profile of the elbow section of the inlet conduit and the starting position and length of the outlet conduit pier is given. The uniformity of the axial velocity distribution on the outlet section of the optimized elbow inlet conduit increases by 3.32%, the weighted average deviation angle decreases by 0.945o, and the hydraulic loss decreases by 10.4%. Compared with the original scheme, the hydraulic loss of the optimized siphon outlet conduit reduces by 7.51%. When the blade angle +2°and the design lift 6.30 m, the flow rate of the prototype pump device is 35.2 m3/s, which meets the design flow requirements, and the efficiency is 76.02%. At the maximum lift of 6.8 m, the flow rate of the prototype pump device is 33.84 m3/s and the efficiency is 75.97%. When the average lift is 5.55 m, the flow rate of the prototype pump device is 36.58 m3/s, and the efficiency is 74.23%. 【Conclusion】 When the main control sizes of the inlet and outlet conduits are not changed, the inlet width of the elbow inlet conduit is only shortened to 2.2D, and the starting position of the siphon outlet conduit pier moves 0.772D to the outlet section and the pier head is perpendicular to the flow direction, the hydraulic efficiency of the pump device in the reconstruction project of Siyang Second Station is relative higher. It ensures the safe, efficient and stable operation of the reconstructed Siyang Second Station. The optimization strategy provides a reference for the reconstruction and optimization of the built pumping station.