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Easy implementation and considerable equipment cost savings, encourage the engineers to use pump as a turbine for both water supply systems and small-scale hydroelectric plants. Flow dynamics in the pumps which are used as turbines are not considered well, and one important disadvantage of them is their incapacity to control flow. This study investigates the mixed-flow dynamics of axial pumps under five operational conditions, from optimal (1.0 QBEP) to the QBEP plus value (20 l/min). In addition, three angles are considered, namely − 3°, 0°, and 3°, to examine the effects of blade angle on them. The flow stability of the axial pump deteriorated as the flow decreased, while pressure pulsations in different flow regions became more intense. Increasing the runner blade angle from − 3° through 0° to 3° influenced the machine's flow and pressure field characteristics. As a result of this increased blade angle, flow unsteadiness and pressure pulsation levels also increased, and the rotor–stator interaction frequencies became dominant in most flow regions. Researchers and engineers will greatly benefit from this study since it contributes to a more thorough understanding of pump flow dynamics.

In this research, to investigate the impact of the guide vanes on the flow analysis in the axial pump, unsteady numerical turbulence field simulations with and without guide vanes are simulated using the model of standard κ–ε turbulence with the technique of sliding mesh (SM). The numerical results are firstly validated and compared with experimental outcomes. Different detailed information data regarding flow analysis, for instance, static, dynamic, total pressures, turbulent kinetic energy, shear stress, and velocity magnitude are qualitatively analysed. Then pressure at varying regions in the pump is qualitatively investigated under different operating conditions. The results have shown that the flow field and performance of the pump are highly affected by adding the guide vane to the axial impeller. The impeller with guide vane can lead to enhance the pump performance. Moreover, results show that the pressure, kinetic energy, shear stress, and velocity are increased by adding a guide vane to the axial impeller. This study will provide good information and guidance to enhance and improve the axial flow pump design operation.

Using computational fluid dynamics method, it was studying the effects of varying flow conditions on internal an axial-flow pump’s main flow characteristics and dynamics. The distribution of mean velocity, turbulent kinetic energy, and pressure variations at various flow rates are analyzed to examine the flow patterns in different flow structures. The simulation outcomes indicate that the vortex’s flow structure and transportation are heavily reliant on the flow, particularly for the extension of a vortex, the emergence of an induced vortex, and the portion of the flow that divides on the tip. At a small flow rate, no tip separation vortex exists. However, as the flow rate increases, and the intensity of tip flows increases. A vortex appears near the leading edge of the blade for an augmented flow rate. Additionally, as the flow rates increase, the leakage vortex core’s radial position moves inward. The main-stream characteristics are also influenced by large flow conditions, especially near the shroud, since more energy is exchanged between main flows as well tip. When flow condition is low, the pump’s head decreases due to greater energy loss. Increasing the flow of pump rises head lift by different times of design flow condition. Consequently, curves of Q-H have obvious positive curvatures. The frequency of the pressure fluctuations observed under high flow conditions is 50 Hz at different monitoring points. Development and evolution laws for the vortex core region are essentially the same as those for the vanes’ streamline figure. Under a design flow rate, the efficiency relative variation was less than 4%.

Axial flow pumps are widely used in water conservancy, petrochemical and agricultural industries. Efficient operation is crucial for energy conservation and emission reduction. Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps, particularly at low flow rates where backflow vortices form near the impeller inlet. This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump. Results show that backflow vortices form when the flow rate decreases to 0.59 Q d . As the flow rate further declines, the backflow vortex progresses upstream, contracts, and rebounds. The flow rate range is divided into three stages: Stage I with no backflow vortex, stage II with initial vortex development extending upstream and relatively fragmented, and stage III with vortex contraction and rebound forming a more coherent structure. Besides, backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 f b . They exhibit a three-dimensional spiral motion involving changes in axial length, self-rotation, and revolution around the pump axis, with an angular velocity of approximately half the impeller’s rotational speed. This work enhances insights into backflow vortex behaviors, which is essential for optimizing pump design and improving operational stability in challenging environments.

Axial flow pumps often experience uneven distribution of axial force on the blades when deviating from design conditions, which can easily lead to local damage to the pump blades. In response to this issue, this article conducts a detailed study on the hydraulic and axial force characteristics of large vertical axial flow pumping stations in China based on constant and non-constant numerical simulation research methods. Research has found that under biased operating conditions, due to the angle between the water flow direction inside the impeller and the impeller blades, the water body collides with the blades, resulting in concentrated pressure distribution on both sides of the inlet side of the impeller blades. Under low flow conditions, the high axial force area of the impeller blade is concentrated in the middle and rear position of the suction surface, while under high flow conditions, the high axial force area is widely distributed. Under the conditions of 0.8 Q to 1.4 Q , the fluctuation of axial force on the impeller blades is mainly affected by the rotation of the impeller blades. However, under low flow conditions, due to the turbulence of the flow state, there is no obvious pattern of axial force variation on the impeller blades. In addition, under different flow conditions, there is no obvious pattern in the fluctuation of axial force on the guide vanes. This also proves that there are problems such as uneven axial force distribution and no periodic changes in the impeller blades under low flow conditions, which can easily lead to damage to the impeller blades. The above analysis can provide some reference for the design of impeller blades.

Rotor-stator interaction in axial pumps can produce pressure fluctuations and further vibrations even damage to the pump system in some extreme case. In this paper, the influence of tip clearance on pressure fluctuations in an axial flow water pump has been investigated by numerical method. Three-dimensional unsteady flow in the axial flow water pump has been simulated with different tip clearances between the impeller blade tip and the casing wall. In addition to monitoring pressure fluctuations at some typical points, a new method based on pressure statistics was proposed to determine pressure fluctuations at all grid nodes inside the whole pump. The comparison shows that the existence of impeller tip clearance magnifies the pressure fluctuations in the impeller region, from the hub to shroud. However, the effect on pressure fluctuation in the diffuser region is not evident. Furthermore, the tip clearance vortex has also been examined under different tip clearances.

When an axial-flow pump works in low flow rate conditions, rotating stall phenomena will probably occur, and the pump will enter hydraulic unsteady conditions. The rotating stall can lead to violent vibration, noise, turbulent flow, and a sharp drop in efficiency. This affects the safety and stability of the pump unit. To study the rotating stall flow characteristics of an axial-flow pump, the steady and unsteady internal flow field in a large vertical axial-flow pump was investigated using 3D computational fluid dynamic (CFD) technology. Numerical calculations were carried out using the Reynolds-averaged Navier–Stokes (RANS) solver and Menter's shear stress transport (SST) k-ω turbulence model. Steady flow characteristics including streamline, velocity vector, pressure and turbulent kinetic energy are presented and analyzed. Unsteady flow characteristics are described using post-processing signals for pressure monitoring points in the time and frequency domains. Using Q-criterion, the locations and evolution rules of the core region of the vortex structure in guide vanes under deep stall conditions were investigated. The reliability of the numerical simulation results was verified using the experimental prototype pressure fluctuation test. In this way, typical flow structure and pressure fluctuation characteristics in an axial-flow pump were analyzed, with contrastive analysis in design condition and stall conditions. Finally, the mechanism of low-frequency pressure fluctuation in a pump unit under the stall condition was revealed.

Due to the unique inlet design of the axial flow pump device with a bell shaped inlet channel, there is currently insufficient quantitative research on its hydraulic characteristics. This study investigates the hydraulic behavior of a vertical axial flow pumping device equipped with a bell-shaped inlet channel, analyzing various blade angles. Energy, cavitation, runaway, and pressure pulsation characteristics were assessed through meticulous testing on a high-precision test bench. Experimental findings indicate that altering the blade angle of the vertical axial flow pumping device with a bell-shaped inlet channel can influence its overall efficiency to some extent. Moreover, as the pump’s blade angle increases incrementally, the device’s cavitation performance gradually diminishes. Pressure pulsation tests reveal a relatively minor amplitude of pressure pulsation at the impeller outlet, contrasting with a more pronounced amplitude observed at the guide vane outlet compared to the pump outlet. These research results provide valuable insights for the design and optimization of actual pumping stations.

The dominant vortex structure near the hub in rotor corner separation flow has an important influence on the internal flow of the axial flow rotating machinery. However, the current quantitative research on the key vortical characteristics of the dominant vortex structure in the corner separation flow is still insufficient. The analysis of the dominant vortex structure (horn-like vortex) in an axial flow pump was conducted and found that the average vortex intensity and turbulence eddy dissipation show a gradual weakening trend along the vortex core line from the corner region to the vortex tail under various working conditions. The evolution of the horn-like vortex in a life cycle includes five stages, inception-growth-development-attachment-decay in the typical working condition 0.62Q 0 . The statistical average frequency of the periodic evolution is about 2.76 times the shaft rotation frequency. The pressure fluctuation near the hub induced by the horn-like vortex increases rapidly and dominates in the flow channel. The average peak-peak value on the impeller outlet section close to the horn-like vortex is about 2.79 times that of the impeller inlet section and should be paid enough attention to.

With the full construction of the South to North Water Diversion Project and the renovation of pumping stations, vertical axial flow pump devices have been widely used in various pumping station projects. This article uses the streamlined method to design the impeller and guide vanes of a vertical axial flow pump device. To analyze the hydraulic and structural characteristics, this paper uses CFD numerical simulation and fluid-structure interaction calculation methods. And the trend of output power change under different flow conditions was divided into three stages, elucidating the reasons for the sudden change in output power under flow conditions of 0.8 Q -1.0 Q . This article focuses on analyzing the internal flow state of the designed lower height guide vane segment to explore the problem of low guide vane height that is prone to occur during the design process. According to the research results, it is found that the lower height guide vane can also play a good role in stabilizing flow and recovering circulation under certain operating conditions. This article also studied the structural characteristics of the impeller and guide vanes, explaining the stress and strain distribution under design flow conditions.