Search Results (15)

A slanted axial-flow pump is extensively applied in coastal pumping stations; however, severe bias flow within the outlet passage will result in unstable operation and low efficiency of the slanted axial flow pump system. In order to mitigate bias flow in a slanted axial-flow pump outlet passage, seven exit setting angle schemes of the guide vanes were designed. The influence mechanisms of the guide vane exit setting angle on internal flow characteristics, hydraulic loss, flow deviation coefficient, vortex evolution patterns, and pump system efficiency were systematically investigated. The results demonstrate that under design flow conditions, as the exit setting angle of the guide vane ranges from 90° to 105°, the flow field in the first half of the guide vane remains essentially the same. The low-velocity region at the guide vane outlet demonstrates initial contraction followed by gradual expansion with increasing stagger angles. Looking downstream within the flow passage from the left to the right, the hydraulic loss in the outlet passage goes up after an initial descending trend as the exit setting angle increases. When the exit setting angle is 97.5°, the bias coefficient of the outlet passage is 1.031. At this point, the vortex core distribution intensity within the outlet passage reaches a minimum, corresponding to the lowest recorded hydraulic loss of 0.230 m. Compared with the original guide vane scheme, the scheme with an angle set at 97.5° can improve the pump system efficiency of the slanted axial flow pump system, whether the flow is set at a design point or at a large point, and the pump system efficiency is increased by 2.3% under design flow conditions. Full article

Hydraulic motors have been widely used in large-scale machinery such as ground heavy equipment and heavy-duty vehicles, ships, and so on because of their high-power drive capability. However, the driving device is confronted with constraints related to its size and weight. Typically, the hydraulic axial piston motor is preferred for its simplicity and efficiency. However, the oil distributor in traditional hydraulic motors faces significant challenges, such as evident oil leakage and power loss from the mating surfaces of the fixed oil distributor and rotating cylinder block. To enhance the reliability and performance of hydraulic motors employed in paper driving applications, this paper introduces a digital radial hydraulic motor used for heavy-duty vehicle traction. The motor is powered by an on-board pump station from which several on/off valves can distribute the hydraulic oil. This design effectively mitigates the performance degradation issues associated with friction and wear in traditional hydraulic motor oil distributors. The drive characteristics of the motor can be flexibly adjusted through the combination of valves. Our investigation into the motor’s design principles and parameter analysis is poised to make an indirect yet significant contribution to the optimization of heavy-duty vehicle traction systems. This paper delineates the application conditions and operational principles of the digital hydraulic motor, thoroughly analyzes the intricate topological interrelationships of its parameters, and meticulously develops a detailed component-level model. Through comprehensive calculations, it reveals the impact of configuration and flow valve parameters on motor efficiency. A simulation model is established for the purpose of verification. Furthermore, the influence of the flow allocation method on efficiency and pressure pulsation is examined, leading to the proposal of a novel flow allocation strategy, the efficacy of which is substantiated through simulation. In conclusion, this paper formulates critical insights to inform the design and selection of components for digital hydraulic motors. These findings may provide a feasible solution for heavy-duty vehicle traction application scenarios. Full article

The exploitation and transportation of deep-sea and remote oil and gas fields have risen to become important components of national energy strategies. The gas–liquid separation and gas blocking caused by the large density difference between the gas and liquid phases are the primary influencing factors for the safe and reliable operation of gas–liquid mixed transportation pump systems. This paper takes the independently designed single-stage helical axial-flow mixed transportation pump compression unit as the research object. Through numerical simulation, the internal flow of the mixed transportation pump is numerically calculated to study the aggregation and conglomeration of small gas clusters in the flow passage hub caused by gas–liquid phase separation, influenced by the shear flow of phase separation, forming axial vortices at the outlet where gas clusters gather in the flow passage. The work performed by the impeller on the gas clusters is insufficient to overcome the adverse pressure gradient formed at the outlet of the flow passage due to the gathering of the liquid phase in adjacent flow passages, resulting in the phenomenon of gas blocking, with vortex gas clusters lingering near the hub wall of the flow passage. Full article

The hydraulic system drives the cutter head mechanism to realize the excavation of large tunnel boring equipment, which puts forward the technical requirements of high pressure and large flow to the pump source. The traditional small displacement axial piston pump uses a planar valve plate. However, under high flow and heavy load conditions, the planar valve plate configuration is prone to uneven wear due to the high-pressure and -velocity (PV) value and pressure shock, which ultimately affects the reliability of the system. A simulation analysis of the load-bearing characteristics of the spherical valve plate mechanism is conducted. The Computational Fluid Dynamics (CFD) method was used to construct flow field models for different valve plate oil film structures to calculate differences in their load-bearing capacities. Additionally, the reasons for variations in load-bearing characteristics based on the curvature radius of the spherical valve plate were analyzed. The simulation results demonstrate that the spherical valve plate exhibits superior leak and load-bearing performance compared to the traditional flat valve plate. Furthermore, the curvature radius of the spherical valve plate directly affects the pulsation characteristics of the piston pump. Smaller curvature radii increase the contact area of the oil film, resulting in greater fluctuation in oil film load-bearing, whereas larger curvature radii lead to increased oil film leakage. Using simulation calculations on heavy-load, high-displacement axial piston pumps, it is determined that the optimal curvature radius for stable load-bearing is 350 mm. Full article

Pump station engineering is a water conservancy project used for long-distance water transfer, irrigation and drainage, and urban living and industrial water supply. Centrifugal pumps are one of the main pump types commonly used in pumping stations, and their operation is of considerable importance for the safety, stability, and efficient operation of pumping stations. This paper takes a large pumping station with seven centrifugal pump units as the research object and combines experimental research and numerical simulation. The axial flow velocity uniformity, average cross-sectional deviation angle, and hydraulic loss of the pump inlet section are evaluated, and the internal flow characteristics of the pump under different startup combination conditions are analyzed based on entropy generation and vorticity. This study also explores the operational performance of the pump station under different startup combination conditions, revealing the mutual influence mechanism between different startup combinations of pump stations and the internal and external characteristics of centrifugal pumps and introducing the optimal startup combination scheme for the pump station system. Research results indicate that the difference in energy loss of centrifugal pumps under different startup combinations is mainly manifested in the impeller and guide vane flow channels. For the two existing inlet flow channel structures in the pump station, the unit effectively operates when the inlet flow channel is tilted to the left. The optimal startup combination method of the pump station under different startup combinations is determined. Full article

Axial-flow pumps consider both the conventional pump mode and the pump as turbine (PAT) mode operation and put forward higher requirements for long-term operation stability and structural strength; therefore, it is of great engineering significance to evaluate the structural strength and fatigue life of the rotor under full operating conditions. In this study, based on computational fluid dynamics and the one-way fluid-structure interaction algorithm, the structural strength and fatigue life of the rotor system of a large vertical axial-flow pump under full operating conditions were evaluated and studied. The results show that blade deformation and equivalent stress are generally higher in the PAT mode than in the pump mode. The maximum deformation in both modes occurs at the tip of the blade, while the area of stress concentration is at the root of the blade. Both the deformation and the equivalent stress increase with increasing flow rate. The minimum safety factor occurs at the blade root in both modes, and the safety factor in the PAT mode is relatively smaller than that in pump mode. Therefore, when designing and manufacturing axial flow pumps for turbine duties, priority should be given to material strength at the blade root during PAT mode operation to ensure safe and stable operation. The aim of this study is to provide technical references and theoretical foundations for evaluating the service cycle of axial-flow pumps and the influence on pump life under different operation modes. Full article

Hydraulic axial piston pumps are the power source of fluid power systems and have important applications in many fields. They have a compact structure, high efficiency, large transmission power, and excellent flow variable performance. However, the crucial components of pumps easily suffer from different faults. It is therefore important to investigate a precise fault identification method to maintain reliability of the system. The use of deep models in feature learning, data mining, automatic identification, and classification has led to the development of novel fault diagnosis methods. In this research, typical faults and wears of the important friction pairs of piston pumps were analyzed. Different working conditions were considered by monitoring outlet pressure signals. To overcome the low efficiency and time-consuming nature of traditional manual parameter tuning, the Bayesian algorithm was introduced for adaptive optimization of an established deep learning model. The proposed method can explore potential fault feature information from the signals and adaptively identify the main fault types. The average diagnostic accuracy was found to reach up to 100%, indicating the ability of the method to detect typical faults of axial piston pumps with high precision. Full article

The large axial flow pump systems used in coastal pump stations are often required to add flap valves to the gates to improve the quality of the transition process. However, due to the unclear mechanism of the additional flap valve on the transition process of the large axial flow pump system, there are many difficulties in the design and application of this feature. In this paper, six kinds of flap valves with different areas are designed. On the basis of the secondary development of the Flomaster software, the transient simulation method is used to study the impact of flap valves with different areas on the large axial flow pump system synchronous start-up process, the asynchronous start-up process, the synchronous stop process and the asynchronous stop process. The research results show that when the AOF is less than 38% A_g during the asynchronous startup, increasing the AOF can significantly improve the shunt ability of the flap valve during startup. However, in the process of asynchronous starting, the working capacity of the flap valve is less affected by the AOF. During the asynchronous shutdown process, the additional flap valve can effectively delay the attenuation of the LAPS flow and reduce the instantaneous head and power. However, when the AOF reaches 38% A_g, further increasing the AOF has no obvious gain in reducing the maximum instantaneous head and power of the LAPS. When the AOF increases from 38% A_g to 49% A_g, the maximum instantaneous head and the power of the LAPS only decrease by 2.7% and 1.4%, respectively. Full article

A large number of operation practices show that the reliability and stability of large axial flow pump systems will face significant challenges during the start-up process. If the start-up control mode or safety auxiliary facilities of large axial flow pump stations are unreasonable, start-up failure will easily follow. In order to find a scientific control strategy for the start-up of large axial flow pump stations, the start-up characteristics of large axial flow pump stations must be fully understood first. In this paper, based on the secondary development of Flowmaster software, a simulation study of the start-up process of a large axial flow pump system equipped with different safety aids is carried out. It is found that it is a very dangerous start-up control mode to delay the opening of the rapid-drop gate to reduce the maximum reflux value and reflux duration when the pump system is initially started. When the rapid-drop gate opens with a delay of 4 s, the power overload coefficient reaches 23.49, indicating that the possibility of start-up failure of the large axial flow pump system increases sharply the longer the gate delay is opened. The method of adding a flap valve to the rapid-drop gate can significantly weaken the instantaneous impact power of the unit and prevent the unit from overload. When safety auxiliary facilities with an additional disc valve on the fast descending gate are adopted, the backflow coefficient is within 0.2, the impact head coefficient is within 2, and the power overload coefficient is less than 0. The research results will provide an important reference value for comprehensively understanding the start-up characteristics of large axial flow pump stations and finding scientific and safe start-up control strategies. Full article

Large axial flow pump systems (LAPS) are widely used in coastal pump stations. In the actual operation of a LAPS, various accidents often occur during shutdown due to the unreasonable control of stop flow measures such as the gate. In this paper, based on the secondary development of Flowmaster numerical software, a numerical simulation study was conducted on the shutdown process of a LAPS with different gate control laws. It was found that the MBV of the shutdown process was greater if the gate was closed more slowly after the unit was powered off. When a 30 s shutdown scheme was used, the MBV during shutdown was 1.63Q_r. When a 60s long shutdown scheme was used, the MBV during shutdown was 1.67Q_r, an increase of 2.45%. When the 150s long shutdown scheme was used, the MVV during the stopping process reached 1.68Q_r, which is an increase of 3.07%. The shutdown method of closing the gate in advance can significantly improve the violent fluctuations of the KCPs of a LAPS during the shutdown transition and will effectively reduce the backflow and the reverse speed of the pump during the shutdown process. Taking the total gate closing time of 120 s as an example, when the 25% gate was closed in advance, the MBV and MRS during the shutdown process were reduced by 14.31% and 1.93%. When the shutdown scenario of preclosing 100% of the gates was adopted, the MBV and MRS during shutdown were reduced by 96.31% and 100%. Full article

Large axial flow pump systems are used in coastal pump stations. It is common and very dangerous for large axial flow pump systems to encounter the failure of the fast hydraulic gate during start-up operations. Methods for equipping LAPS with reasonable safety aids for start-up operations in order to deal with the unexpected situation that the quick gate cannot be opened, limiting the safety and stability of LAPS, have become a key focus of research. We aim to investigate the effect of safety aids on the LAPS’s start-up characteristics under gate rejection conditions and to find the best safety aid allocation method to solve the LAPS’s start-up failure problem. Based on the verification of the model test, a numerical simulation of the start-up process of the large axial flow pump system equipped with auxiliary safety features was carried out under the condition of gate rejection. The results show that under the condition of gate rejection, the auxiliary FLVA or OVHO can help LAPS reduce the risk of start-up failure to a certain extent. The FLVA will play the main protective role during the start-up operations of the LAPS if the LAPS is equipped with both the OVHO and FLVA of unrestricted size under the gate rejection condition. LAPS equipped with OVHO (1.27 H_m) and FLVA (49.1% A_g) and LAPS equipped with FLVA (49.1% A_g) have comparable start-up safety. The latter has an His of 1.783 H_r and a P_is of 1.30 Pr. The former has an instantaneous shock head of 1.772 H_r and a P_is of 1.30 P_r, which exhibit a decrease of 0.38% and 0 %, respectively. The research results will provide an important reference value for the prevention of pump station start-up failures under gate rejection conditions. Full article

The periodic flow and pressure pulsation of the axial piston pump can lead to periodic vibration, noise, and even damage to various components in the hydraulic system. Therefore, the dynamic characteristics analysis of the axial piston pump in the hydraulic system is of great significance for reducing vibration and noise in the hydraulic system and improving efficiency. The double-compound axial piston pump is the key component of a high power and large flow hydraulic power system, which has a special power control mode. In this paper, the working and control principles of the double-compound axial piston pump are analyzed, the numerical model of the double-compound axial piston pump is established, and the effectiveness of the model is verified through experimental tests. The constant power control characteristics of the double-compound axial piston pump under different power settings and the variable power control characteristics under the rated load pressure are analyzed. By analyzing the dynamic characteristics of the double-compound axial piston pump, the influence of different working conditions on the dynamic characteristics is investigated. The results show that the output efficiency of the double-compound axial piston pump is higher when the output flow is larger. When the piston chamber works in the closed pre-compression pressure zone and the closed pre-release pressure zone, oil backflow occurs. The oil backflow in the piston chamber seriously intensifies the outlet flow pulsation of the double-compound axial piston pump. The flow pulsation rate is positively correlated with load pressure and power control pilot pressure, while negatively correlated with spindle speed. The paper provides a basis for the analysis and optimization of power control, flow pulsation, fluid vibration, and noise of the double-compound axial piston pump. Full article

The recovery of excess energy in water supply networks has been a topic of paramount importance in recent literature. In pressurized systems, a pump used in inverse mode (Pump As Turbine, PAT) demonstrated to be a very economical and reliable solution, compared to traditional energy production devices (EPDs). Due to the large variability of flow rate and head drop within water distribution networks, the operation of PATs could be performed by a series-parallel regulation system based on an electronic or a hydraulic principle. Despite the low cost of the PATs and of regulation and control systems, a great barrier to the diffusion of a small hydro power plant in water distribution is represented by the necessity of additional civil works to host the whole plant. Based on laboratory and numerical experiments, the present paper proposes a new low-cost technology, overcoming most of the limitations of the present technologies when low energy is available and high discharge variation occurs. The operating conditions of the plant are properly optimized with reference to the working conditions of a case study. Despite the laboratory prototype having exhibited a significantly low efficiency (i.e., 16%), due to the use of small centrifugal pumps suitable for the analyzed case study, in larger power plants relying on more efficient semi-axial submersed pumps, the energy conversion ratio can increase up to 40%. The results of this research could be useful for network managers and technicians interested in increasing the energy efficiency of the network and in recovering energy in the peripheral branches of the network were a large variability of small flow rates are present. Full article

Increasing extreme rainfall events caused by global climate change have had a significant impact on urban drainage systems. As a critical component of a pumping station, a large-scale slanted axial-flow pump (SAFP) featuring high specific speed plays a critical role in mitigating urban flooding and waterlogging. In this study, to reveal the transient characteristics of a SAFP at shut-off conditions, a computational fluid dynamics (CFD) based approach with dynamic mesh was proposed. Multiple shut-off conditions with various shut-down speeds of the sluice gate (SG) were modeled. Our analysis demonstrated that both the shut-off conditions and the slanted structure have conspicuous impacts on the hydrodynamic performance of a SAFP. Reducing the shut-down speed leads to a greater reverse flow rate and higher runner speed. The water hammer effect was simulated with different shut-down speeds, increasing the water head by 5.07–10.42 m, the axial force by 163.46–297.06 kN∙m, and the axial moment by 116.05–224.01 kN∙m. Compared with the axial direction, moments in the radial directions were found with more obvious oscillation as a result of stronger rotor–stator interaction. Due to the gravitational effect of the slanted structure, the fluctuation of the runner in vertical direction presented an off-axis characteristic compared with the horizontal one. As the SG speed increased, pressure fluctuations gradually decreased at various locations across the SAFP. Full article

The slurry transport pump is the key equipment of deep-ocean mining systems. The motion law of coarse particles in the pump is not clear enough. In this paper, a hydraulic model of a laboratory-scale two-stage slurry transport pump is constructed, and the motion characteristics of coarse particles in the pump are numerically studied by using the computational fluid dynamics–discrete element method (CFD-DEM) method. The performance curve of the pump is obtained by experimental measurement, and the reliability of the calculated results is verified. Due to the application of the amplification flow rate design method, the optimum efficiency point of the pump is shifted to the large flow rate condition. Differences in particle swarm within two stages are compared. The position distribution, velocity variation and trajectory of particles in the impeller and bowl diffuser are studied in detail. The velocity of particles leaving the impeller depends on whether they collide with the impeller blade. The motion of particles in the bowl diffuser is divided into three periods. Collision between particles and blades in the bowl diffuser not only leads to energy loss but also gradually transforms the circumferential velocity of particles into axial velocity in the second period. This work can provide a reference for the study of wear and blockage prevention of slurry transport pumps. Full article