Search Results (17)

High-speed mixed-flow and axial-flow pumps often exhibit hump or double-hump patterns in flow–head curves. Operating in the hump region can cause flow disturbances, increased vibration, and noise in pumps and systems. Variable-speed ship navigation requires waterjet propulsion pumps to adjust speeds. Speed transitions can lead pumps into the hump region, impacting efficient and quiet operation. This paper focuses on mixed-flow waterjet propulsion pumps with guide vanes. Energy, entropy production, and flow characteristic analyses investigate hump formation and internal flow properties. High-speed photography in cavitation experiments focuses on increased vibration and noise in the hump region. This study shows that in hump formation, impeller work capacity decreases less than internal fluid loss in the pump. These factors lead to an abnormal increase in the energy curve. The impeller blades show higher pressure at peak conditions than in valley conditions. Valley conditions show more pressure and velocity distribution variance in impeller flow passages, with notable low-pressure areas. This research aids in understanding pump hump phenomena, addressing flow disturbances, vibration, noise, and supporting design optimization. Full article

During pump operation, the pump-turbine system experiences unstable fluctuations in outlet pressure, which induces turbulence and additional energy losses. Understanding the impact of outlet pressure variations on the internal flow field is crucial for the further development of turbine units. This study employs numerical methods to systematically analyze the effects of outlet pressure changes on flow characteristics and energy loss. The results show that a decrease in outlet pressure to P0.9BEP significantly increases entropy production in the double-row stay guide vane region, primarily due to flow separation and vortex formation. In the flow passage, sealing gap, and tailpipe regions, entropy production is mainly driven by wall effects, while secondary flows influence the spiral case. The vortex distribution in the double-row stay guide vane is complex, with different variation trends observed in the active and fixed guide vane regions. Outlet pressure changes affect the interaction between the flow passage blades and the fluid, leading to localized flow separation and directly impacting energy loss in downstream components. Additionally, the rate of change in outlet pressure significantly influences vortex generation and dissipation. This research provides new theoretical insights and research directions for performance optimization and energy loss control in pump-turbine systems. Full article

The residential sector is one of the main sectors responsible for the atmospheric emission of CO₂. Hence, a significant effort is required to develop technological solutions to enable decarbonization. The integration of Organic Rankine Cycle (ORC)-based units with renewable sources at a micro-scale of cogeneration units is commonly believed to be one of the most important technological alternatives. Indeed, an ORC-based unit allows the exploitation of low-temperature heat sources in the production of electricity. The low power scale of this application (1–5 kW) and the severe operating conditions call for the reliable and proper design of components. Particularly critical is the pump, as the experimental analyses available in the literature show its efficiency rarely exceeds values of 0.3. The most suitable technology is volumetric, and among those available, the sliding vane types are interesting candidates. However, low efficiency leads to a significant erosion of the power produced by the expander, limiting the achievement of high-efficiency values. What is more, in the literature, there is a lack of development of optimization strategies to improve the performance of this machine. To fill this knowledge gap, in this present paper an optimized sliding vane rotary pump was designed. Thanks to a comprehensive experimentally validated model, the pump performance was assessed for a wide range of operating conditions. Results confirmed that a disk-shaped configuration also ensures the best efficiency is achieved for small-scale pumps. Moreover, the model allowed for a detailed analysis of efficiency, evaluating the volumetric, fluid dynamic and mechanical behaviors. Results demonstrated that the weakest point was the mechanical efficiency, which was between 0.45 and 0.55. The best configuration was that involving four blades, the adoption of graphite and a clearance gap between the rotor face and casing of 10 μm. These design solutions improved efficiency by up to 25%, with a maximum value equal to 0.50, which is close to double with respect to the usual values. A final remark concerns the operating robustness of the machine, as the efficiency demonstrated weak variations even when wide operating conditions were considered. Full article

The pump turbine, as the core equipment of a pumped storage power plant, is most likely to operate in the hump zone between condition changes, which has a great impact on the stable operation of the power plant, and the high sedimentation of a natural river will lead to wear and tear in the overflow components of the equipment. Therefore, this paper is based on the Euler–Lagrange model, and seeks to investigate the distribution of vortices in the hump zone of the pump turbine and its effect on the movement of sand particles. The study shows that as the flow rate increases, the strip vortex in the straight cone section of the draft tube becomes elongated, and the cluster vortex in the elbow tube section gradually decreases. The strip vortex encourages the sand particles to move along its surface, while the cluster vortex hinders the movement of the sand particles. The accumulation areas of the sand particles in the straight cone section and the elbow tube section increase axially and laterally, respectively. The blade vortex in the runner gradually occupies the flow channel as the flow rate increases, and the blade vortex near the pressure surface encourages the sand particles to move towards the suction surface, resulting in the serious accumulation of sand particles on the suction surface. As the flow rate increases, the number of blades where sand particles accumulate increases and the accumulation area moves towards the cover plate and the outlet. The flow separation vortex in the double-row cascade decreases as the flow rate increases, which drives the sand movement in the middle and lower sections of the vanes. The area of sand accumulation in the stay vane decreases with increasing flow rate, but the area of sand accumulation between the guide vanes increases and then decreases. The vortex on the wall surface of the volute gradually decreases with the flow rate, and the vortex zone at the outlet first decreases, then disappears, and finally reappears. The vortex at the wall surface suppresses the sand movement, and its sand accumulation area changes from elongated to lumpy and finally to elongated due to the increase in flow. The results of the study provide an important theoretical reference for reducing the wear of pump turbine overflow components. Full article

To investigate the hydraulic characteristics during the start-up process of a full-flow pumped storage unit under low-head conditions, numerical simulations were conducted to study the dynamic characteristics during the process, providing a detailed analysis of the dynamic behavior of the internal flow field during the transition period as well as the associated variation in external performance parameters. Study results revealed a vortex-shedding phenomenon during the initial phase of the start-up process. These vortices restrict the flow, initiating a water hammer effect that abruptly elevates the upstream pressure within the runner. As the high-pressure water hammer dissipated, the flow rate rapidly increased, leading to a secondary but relatively weaker water hammer effect, which caused a momentary drop in pressure. This series of events ultimately resulted in significant oscillations in the unit’s head. After the guide vanes stop opening, the vortex structures at the runner inlet and outlet gradually weaken. As the runner torque continues to decline, the unit gradually approaches a no-load condition and enters the S-shaped region. Concurrently, pressure pulsations intensify, and unstable vortex formations reemerge along the leading and trailing edges of the runner blades. The escalated flow velocity at the runner’s exit contributes to the elongation of the vortex band within the draft tube, ultimately configuring a double-layer vortex structure around the central region and the pipe walls. This configuration of vortices precipitates the no-load instability phenomenon experienced by the unit. Full article

This paper introduces the prototype design, magnetic field analysis and experimental test of a double-rotating ferrofluid vane micropump with an embedded fixed magnet. The micropump is based on the working principle of a positive-displacement pump, as well as the magnetic characteristics and flow properties of magnetic fluid. Through the numerical analysis of the pump cavity magnetic field and the experimental test, the structural parameters of the micropump are optimized reasonably. The pumping flow and pumping height of the micropump were characterized at different driving speeds. The maximum pumping flow rate is approximately 410 μL/min, and the maximum pumping height is approximately 111.4 mm water column. The micropump retains the advantages of simple structure, easy manufacture, flexible control, self-sealing, self-lubrication, low heat production, etc., and can block the pumped liquid backflow. The resulting double-rotating ferrofluid blades can improve pumping efficiency and pumping capacity, and can improve pumping reliability and stability to a certain extent. Full article

In order to study the influence of impeller structural parameters on the hydraulic performance and casting moulding of spiral centrifugal pumps, this paper selects a double vane spiral centrifugal pump with a specific rotation number of 170 as the research object. The Plackett–Burman experimental design is used to screen the influencing factors, and the results show that the vane thickness and the impeller outlet width are the significant influencing factors. Based on this result, five different scenarios were set for these two key parameters, numerical calculations were carried out using numerical simulation software for each of the five flow ratio cases, and casting simulations were carried out for the model of each scenario using AnyCasting6.0 to analyze the influence of these two factors on the hydraulic performance and casting forming of the spiral centrifugal pump. It was found that in terms of vane thickness, a moderate increase in vane thickness improved the hydraulic performance at small flow rates, but an excessive increase at large flow rates led to a decrease in efficiency and an increase in the probability of casting defects. In terms of impeller outlet width, increasing the outlet width caused the design point to be shifted, leading to a decrease in efficiency at small flow rates, but an increase in efficiency when the design flow rate was higher. At the same time, increasing the outlet width makes casting defects more likely to occur at the blade and back cover joint than on the blade surface. The study in this paper clarifies the significant effects of these two parameters on the performance and casting quality of spiral centrifugal pumps, and provides guidance for the optimal design of spiral centrifugal pumps. Full article

Stall usually occurs in the hump area of the head curve, which will block the channel and aggravate the pump vibration. For centrifugal pumps with guide vanes usually have a clocking effect, the stall characteristic at different clocking positions should be focused. In this paper, the flow field of the centrifugal pump under stall conditions is numerically simulated, and the rotor–stator interaction effects of the centrifugal pump under stall conditions are studied. The double-hump characteristic is found in the head curve by using SAS (Scale Adaptive Simulation) model. The hump area close to the optimal working condition is caused by hydraulic loss, while the hump area far away from the optimal working condition point is caused by the combined action of Euler’s head and hydraulic loss. The SAS model can accurately calculate the wall friction loss, thus predicting the double-hump phenomenon. The pressure fluctuation and head characteristics at different clocking positions under stall conditions are obtained. It is found that when the guide vanes outlet in line with the volute tongue, the corresponding head is the highest, and the pressure fluctuation is the lowest. The mechanism of the clocking effect in the centrifugal pump with guide vanes is obtained by simplifying the hydrofoil. It is found that when the downstream hydrofoil leading edge is always interfered with by the upstream hydrofoil wake, the wake with low energy mixes the boundary layer with low energy, which causes small-pressure pulsation. The results could be used for the operation of centrifugal pumps with guide vanes. Full article

Guide vanes (GVs) are installed between the runner and the stay vanes for flow guidance and discharge regulation in reversible pump-turbines. The unstable torsional self-excited vibration of the guide vane (GV) may occur when running at small guide vane opening angles during the transient operations involving pump flow. In addition, the double-stage radial vanes may induce complex flow in the vanes and influence the stability of torsional self-excited vibration of the guide vane. In this study, numerical simulations were conducted at small guide vane opening angles in pump mode for two different guide vanes based on the three-dimensional computational fluid dynamics (CFD) method. The flow regime with a deflection was formed on the trailing edge with a circle in the vaneless region that rotated reversely against the runner rotation when operating at smaller guide vane opening angles for both of the two guide vanes. Based on this, the coupling simulations based on the CFD method with a single-degree-of-freedom (1DOF) oscillator were carried out under these operating conditions. Two flow types were formed at small opening angles when adopting different inlet boundary conditions. The results showed the flow regime with a deflection on the trailing edge may aggravate the instability of torsional vibration when applied as an initial flow field. Moreover, the vibration instability of the torsional self-excitation for two guide vanes was analyzed, showing that modifying the profile of guide vane airfoil is an efficient and reliable approach for weakening the torsional vibration instability. Full article

Regenerative flow machines are known to be simple in construction but complex in flow characteristics. Due to this reason, the design of these machines has been primarily esoteric, and hence its performance heavily relies on the experience and expertise of the designer. Since there are no established rules of thumb for designing them, this paper attempts to provide simple design correlations for systematically designing regenerative flow machines viz. pumps, blowers, and compressors. Three different impeller designs have been considered, namely the (i) single-side vane impeller, (ii) double-side vane impeller, and (iii) peripheral vane impeller, for the three types of machines. More than ten design parameters have been considered for sizing the machines. Experimental and computational data available in open literature have been used to obtain physically meaningful correlations in simple form, and require minimal and practically available inputs. Fluid properties and practical constraints were taken into consideration while deriving the correlations. Constants in the correlations were obtained using least square regression analysis. The accuracy of the obtained correlation is determined by the correlation coefficient. The deviation obtained using the derived correlations varied from 10 to 25%. A consolidated set of correlations has been presented, which will be helpful in making a preliminary design before CFD simulation, design optimization, and prototype building. Finally, the obtained correlations have been used to demonstrate the design of a regenerative flow pump. Full article

In order to improve the anti-wear performance of a double-vane self-priming centrifugal pump during two-phase flow transfer, the construction of a streamline groove structure at the outlet end of the suction side of the vane, based on the bionic principle, is proposed. Different pump characteristics are analysed to investigate the effect of different bionic groove spacing on the resistance to particle wear and the mechanism of improvement of the bionic grooves. The results show that the effect of the bionic blades on the hydraulic characteristics of the pump is within the allowable error (±1.4%). The circular groove structure with different spacing produces a difference in the pressure distribution on the blade. At the same particle concentration, with the increase in the groove spacing distance, the average wear of the blades first decreases and then increases; the average wear rate at the spacing of 7 mm is the smallest. At a particle concentration of 90 kg/m³, the average wear rate at a groove spacing of 7 mm is ~0.63 × 10⁻⁴ kg/s∙m², and the wear area is mainly found in the middle of the blade. The reason why the bionic blade improves the anti-wear performance of the pump is due to the reverse vortex zone in the groove, which changes the particle trajectory and collision frequency. The bionic grooves with a diameter of 2 mm and a spacing of 7 mm significantly reduce the average wear rate of the pump at different particle concentrations, while maintaining hydraulic performance. Full article

The article presents an innovative design solution of a balanced vane pump integrated with an electric motor that has been developed by the authors. The designed and constructed bench, which enables testing of the system: power supply, converter, ntegrated motor—pump assembly and hydraulic load at different motor speeds and different pressures in the hydraulic system, is described. The electromagnetic and hydraulic processes in the motor-pump unit are investigated, and new, previously unpublished, results of experimental studies at steady and dynamic states are presented. The results of the study showed good dynamics of the integrated motor-pump assembly and proved its suitability to control the pump flow rate, and thus, the speed of the hydraulic cylinder or the speed of the hydraulic motor. Full article

A multistage centrifugal pump was developed for high head and high flow rate applications. A double-suction impeller and a twin-volute were installed at the first stage followed by an impeller, diffuser and return vanes for the next four stages. An initial design feasibility study was conducted using three-dimensional computational fluid dynamics tools to study the performance and the hydraulic losses associated with the design. Substantial losses in head and efficiency were observed at the interface between the first stage volute and the second stage impeller. An inducer-type guide vane (ITGV) was installed at this location to mitigate the losses by reducing the circumferential velocity of the fluid exiting the volute. The ITGV regulated the pre-swirl of the fluid entering the second stage impeller. The pump with and without ITGV is compared at the design flow rate. The pump with ITGV increased the stage head by 63.28% and stage efficiency by 47.17% at the second stage. As a result, the overall performance of the pump increased by 5.78% and 3.94% in head and efficiency, respectively, at the design point. The ITGV has a significant impact on decreasing losses at both design and off-design conditions. An in-depth flow dynamic analysis at the inducer-impeller interface is also presented. Full article

A multistage centrifugal pump is designed for pumping low-viscosity, highly volatile and flammable chemicals, including hydrocarbons, for high head requirements. The five-stage centrifugal pump consists of a double-suction impeller at the first stage followed by a twin volute. The impellers for stages two through five are single-suction impellers followed by diffuser vanes and return channel vanes. The analytical performance is calculated initially in the design stage by applying similarity laws to an existing scaled-down pump model designed for low flow rate applications. The proposed pump design is investigated using computational fluid dynamics tools to study its performance in design and off-design conditions for water as the base fluid. The design feasibility of the centrifugal pump is tested for other fluids, such as water at a high temperature and pressure, diesel and debutanized diesel. The pump design is found to be suitable for a variety of fluids and operating ranges. The losses in the pump are analyzed in each stage at the best efficiency point. The losses in efficiency and head are observed to be higher in the second stage than in other stages. The detailed flow behavior at the second stage is studied to identify the root cause of the losses. Design modifications are recommended to diminish the losses and improve the overall performance of the pump. Full article

The unsteady flow process of waterjet pumps is related to the comprehensive performance and phenomenon of rotating stall and cavitation. To analyze the unsteady flow process on the unsteady condition, a computational domain containing nozzle, impeller, outlet guide vane (OGV), and shaft is established. The surface vortex of the blade is unstable at the valley point of the hydraulic unstable zone. The vortex core and morphological characteristics of the vortex will change in a small range with time. The flow of the best efficiency point and the start point of the hydraulic unstable zone on each turbo surface is relatively stable. At the valley point of the hydraulic unstable zone, the flow and pressure fields are unstable, which causes the flow on each turbo surface to change with time. The hydraulic performance parameters are measured by establishing the double cycle test loop of a waterjet propulsion device compared with numerical simulated data. The verification results show that the numerical simulation method is credible. In this paper, the outcome is helpful to comprehend the unsteady flow mechanism in the pump of waterjet propulsion devices, and improve and benefit their design and comprehensive performance. Full article