Pump Flow Research Articles

Advances in Flow Control Methods for Pump-Stall Suppression: Passive and Active Approaches

This article provides a comprehensive review of key approaches to suppressing stall flow in pumps, offering insights to enhance pump performance and reliability. It begins by outlining the formation mechanisms and characteristics of stalls, followed by an in-depth analysis of various stall types. The discussion highlights passive and active flow control methods, emphasizing their roles in suppressing stall phenomena. Passive flow-control strategies, including surface roughness, grooves, obstacles, fixed guide vanes, and vortex generators, are examined with a focus on their mechanisms and effectiveness in suppressing stall. Similarly, active flow-control techniques, such as jets and adjustable guide vanes, are explored for their capacity to regulate the flow field and suppress stall. The novelty of this review lies in its exploration of the effectiveness of passive and active flow-control methods in suppressing pump stall, with a focus on their mechanisms of action and the underlying principles of stall formation. The findings reveal that appropriate flow-control measures can mitigate laminar flow separation and reduce performance losses associated with stall. However, careful attention must be given to the optimal arrangement of control devices. Finally, the article highlights the limitations of current implementations of combined active and passive flow-control methods while offering insights into the future potential of advanced flow-control technologies in regard to suppressing stall.

A fish-friendly axial flow pump turns out to be eel safe, roach unfriendly and bream unsafe

Additional and refurbished pumping stations are required to mitigate the intensifying occurrence of droughts and floodings. These installations negatively impact threatened freshwater fish populations due to the increased risk of injury and mortality when fish pass through them. Fish-friendly pumping installations have been proposed as a potential solution to reduce these risks. However, published assessments of these new types of pumps remains lacking, and the few available studies do not enable a cross-comparison with conventional pump types. The promising, yet understudied, Fairbank Nijhuis ‘fish-friendly’ axial flow pump has been assessed in previous works, however the results remain ambiguous due to low recapture rates, unconsidered parameters, fixed operating conditions, and the inability to identify the likely sources of injury and mortality. In this study, we address the limitations of previous works by implementing a standardized protocol for live fish in conjunction with passive barotrauma detection sensors. The major finding of this work is that safe passage of eel (100% survival) is confirmed, but that bream and roach had a much lower survival probability (24% and 70% survival respectively) than expected, albeit higher than for a conventional axial flow pump (roach survival: 13%). Furthermore, roach and bream passing at higher rpm suffered significantly higher mortalities. The impact of the impeller was found to be the most common source of severe injury for both pumps. These results are significant because they conclusively show that fish-friendly pumps may be considered safe for eel, but not for other endemic European fish species such as roach and bream.

Modeling Investigation on Gas Backflow Performances in Screw Vacuum Pump

Rotor structure has a great influence on the gas backflow in a screw vacuum pump. The characteristics of the gas main flow along the spiral groove of the screw rotor and the gas reverse flow along the tooth-shaped, tooth side, radial, and circumferential clearances are investigated. A new mathematical model of the pumping flow and backflow involved in a flow balance model is proposed to investigate the actions of the shearing force and pressure difference force. The calculated backflow is verified by comparing the experimental measured results. The relationships of the structural parameters of the screw rotor are established. The effects of the rotor parameters, such as pitch, diameter, and compression ratio, on backflow are revealed. The results show that the rotor diameter and compression ratio remain constant and that the influence of pitch on the backflow is slightly weak, with backflow variations of less than 3%, whereas the pitch, rotor length, and compression ratio are constant and the rotor addendum diameter is directly proportional to the backflow. The addendum diameter of rotor #4 is the largest, and its backflow is about 1.5 times larger than that of rotor #1. When the rotor radial sizes and the pitch of the suction end are constant, the compression ratio is inversely proportional to the backflow in the low-pressure region and proportional to the backflow in the high-pressure regions. Therefore, for a vacuum pump operating in low-pressure areas, the use of the compression ratio of 2.2 or higher is favorable for the reduction in backflow.

Study on the particle dynamic characteristics in a centrifugal pump based on an improved computational fluid dynamics-discrete element model

To accurately investigate the solid–liquid flow mechanisms within the pump, this study employs an improved Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach to examine the solid–liquid interactions in a centrifugal pump. First, the improved CFD-DEM is introduced, focusing on turbulence dissipation near the wall and velocity reconstruction. Then, a comparison is made between the CFD-DEM's performance before and after the enhancements. Finally, an analysis is conducted on how the dynamic characteristics of particles within the pump vary under different solid phase concentration conditions. The study revealed that the particle distribution from the corrected CFD-DEM aligns more closely with the experimental results. At a 2% concentration under the design conditions, the head error was reduced by 0.476%, while the efficiency error decreased by 0.076%. Additionally, as the solid phase concentration increased, there was a corresponding rise in the impact power loss of the particles, dissipative power loss, collision frequency, peak values of particle collisions, and the degree of overlap during these collisions. The comparison revealed that the pressure gradient force has the most significant impact on particle motion. As the pressure gradient force increases, the shear power dissipation of the particles also rises. For solid phase concentrations ranging from 1% to 4%, the average shear power variation during the computation period is between 4.28 × 10−6 W and 5.68 × 10−6 W. As the solid phase concentration increases, the volume fraction of the solid phase distribution on the component wall also gradually rises. These findings provide valuable insights for enhancing the accuracy of research on solid–liquid flow in centrifugal pumps.

Influence of side channel inlet angle on energy conversion of a side channel pump

The side channel pump generates several disadvantage vortices due to abrupt structural changes at the junction of the impeller and side channel, leading to unstable flow, which may induce severe vortex cavitation at the inlet section of the side channel, its impact on the pump's unstable flow mechanism and on the energy conversion characteristics has yet to be thoroughly investigated. This paper explores the effect of backflow vortex on pump performance through optimizing side channel inlet angles by combining the Ω criterion, helicity, and entropy production methods. The computational fluid dynamics numerical simulation's accuracy has been experimentally verified. It was found that increasing the side channel inlet angle could improve internal flow, thereby suppressing backflow vortices and promoting dynamic vortices formation in the inlet section. The backflow vortex is the primary source of high localized energy loss in the inlet section, significantly influencing the reduction of flow loss. It also reduces low pressure areas caused by backflow vortices, thus, restricting cavitation origin. In addition, within a certain range, the flat side channel pump enhances its hydraulic performance, exhibiting the best performance at a 60° inlet angle with an efficiency improvement of 4.6% at the Best Efficiency Flow Point (BEP), which has the most effective backflow vortex suppression, and therefore, lowest flow losses. However, the head improvement was negligible. The performance improvement is due to complete energy conversion within the inlet section. This paper offers new insights into the mechanisms underlying internal energy loss and cavitation characteristics in refining side channel pumps.

Numerical simulation study of vortex cavitation and induced pulsation characteristics in spiral lobe pumps

Lobe pumps are used in many different sectors because of their versatility and effectiveness for managing multiphase flows. In this study, three-dimensional unsteady numerical simulations are performed to evaluate the vortex cavitation phenomenon in these pumps. The work combines dynamic meshing techniques, advanced vortex recognition methods, and a full cavitation model to provide insight into the genesis, evolution, and influence of vortex cavitation on pump performance. The results of the study demonstrate that under high-speed and high-pressure conditions, vortex flow occurs at the edge of the rear of the rotor lobe in the suction chamber of the lobe pump, resulting in the production of vortex cavitation. Cavitation is most strong at the core of the vortex, while the degree of cavitation at the edge of the vortex gradually diminished. The gas volume fraction reduces from 0.135 to 0.0832, and this makes the pressure decrease from 1.055 to 1.02 MP. The process of genesis, development, and removal of vortex cavitation is cyclic. At different levels of cavitation, the degree of pulsation in pump outlet flow, pressure, and radial force increases with increasing cavitation. Periodic vortex cavitation leads to periodic changes in pump output pressure, flow rate, radial force, and axial force.

The performance analysis of a compressed air energy storage (CAES) for peak moving with cooling, Heating, and power production

This study focuses on modeling and optimizing a multifaceted geothermal-based energy production system within the context of Denmark. The primary objectives revolve around enhancing system efficiency and reducing operational costs. The system under investigation comprises geothermal components, an organic Rankine cycle, a compressed air energy storage facility, and an absorption chiller. The organic Rankine cycle operates using refrigerants R123 and ammonia, effectively converting thermal energy into electricity and thermal energy for various applications. Optimization was carried out employing the Response Surface Method in tandem with Design-Expert software, facilitating the fine-tuning of objective functions. Two key objectives were selected: Exergy Round Trip Efficiency and cost rate, aimed at improving technical performance and curbing economic expenditure. A range of design variables were considered for optimization, including turbine and pump inlet temperatures, geothermal mass flow rate, turbine and pump efficiencies, compressor and gas turbine efficiency, inlet pressure to the compressed air energy storage tank, and evaporator pinch point temperature. The system reached an impressive exergy efficiency peak of 77.98%, accompanied by a modest cost rate of 5.48 $/h. The costliest components in the system were the compressed air energy storage unit, followed closely by organic Rankine cycle 1 and organic Rankine cycle 2. In contemplating the practical implementation of this innovative energy system, ten cities in Denmark underwent rigorous analysis, accounting for technical and economic factors. Subsequent assessments identified Aarhus as the optimal location to initiate the system. The environmental results showed that by producing 13981.9 megawatts of electricity annually in Arhus City, it is possible to help reduce CO2 emissions by 2853.2 tons of CO2/year and avoid environmental costs of 68455.3 $/year. The environmental assessment also highlighted the potential for substantial green space expansion, estimating an additional 13 hectares of green areas in the city of Aarhus, Denmark.

Robust cavitation-based pumping into a capillary

Cavitation bubbles collapsing near boundaries create liquid flow through their center of mass movement, the formation of liquid jets, and long living vorticities. Here, we demonstrate robust pumping of the liquid with a compact and simple geometry, the open end of a thin-walled circular capillary tube filled with liquid. We study the dynamics of the cavitation bubbles and report on the resultant microjet formation through experiments and simulations. In the experiments, the dynamics of laser-induced cavitation bubbles are captured with high-speed microscopy. Simulations show excellent agreement with the experiments. The jet flow pumps liquid flow toward the capillary opening. The simulation reveals that, in the current study range, both the non-dimensional inner diameter of the capillary and the non-dimensional stand-off distance show influences on the jet width, and only the non-dimensional stand-off distance affects the maximum jet velocities. The results demonstrate that the confinement of the bubble within the capillary alters the anisotropic pressure field around the bubble, leading to a more mild collapse.

Increased electrolyte flow resistance and blockage due to hydrogen evolution in a flow battery single cell under stack electrolyte feeding conditions

In a flow battery stack, individual cells are typically fed with electrolyte in a parallel configuration, resulting in identical pressure drops across each cell. In this parallel liquid supply system, the distribution of electrolyte flow is closely related to the flow resistance in each branch. During operation, gas bubbles generated by chemical and physical processes tend to accumulate in the electrode pores, obstructing electrolyte flow and leading to uneven electrolyte distribution. Previous studies have mainly focused on single-cell experiments using constant flow pumps, which differ significantly from the nearly constant pressure difference liquid supply within the stack electrodes. To investigate the effects of gas evolution on liquid flow under constant pressure difference conditions, we propose a gravity-driven electrolyte feeding system for testing in a single cell, which simulates the flow conditions encountered in real stack applications. Under the interaction between gas bubbles and liquid flow, hydrogen evolution reactions at the scale of “mA cm-2” significantly reduce the electrolyte flow through the porous electrode. When the pressure difference drops below a critical threshold, the electrolyte flow rate continues to decrease significantly and may even stop entirely. And a sufficient feeding pressure difference is essential for enhancing bubble removal efficiency.

Inflammatory and Hemolytic Responses of Microaxial Flow Pump Temporary Ventricular Assist Devices via Axillary Access in Cardiogenic Shock

Inflammatory and Hemolytic Responses of Microaxial Flow Pump Temporary Ventricular Assist Devices via Axillary Access in Cardiogenic Shock

Optimization of Centrifugal Pump Properties to Improve the Accuracy of Water Discharge and Pump Head Measurements

Centrifugal pumps are extensively used in industries and water management systems, where accurate measurements of water flow rate and pump head are essential for evaluating performance. However, inaccuracies arising from suboptimal designs of training kits present challenges in educational environments. This study aimed to optimize a centrifugal pump training kit to enhance measurement accuracy and reliability. The research was conducted over four months, involving modifications to the impeller, casing, and pressure measurement systems, along with rigorous calibration to minimize errors. Measurements of suction pressure, discharge pressure, water flow rate, and pump head were repeated under standardized conditions to ensure data consistency. The results demonstrated significant improvements, with consistent measurements of suction pressure (21 inHg), discharge pressure (15 PSI), water flow rate (0.5 L/s), and pump head (1.38 mH₂O). These optimizations reduced system inefficiencies, such as backflow and turbulence, and enhanced the kit’s ability to replicate real-world operating conditions. The improved training kit provides students with a reliable tool for practical learning, bridging theoretical concepts with real-world applications in fluid mechanics. This study underscores the importance of continual enhancement of laboratory teaching tools to support effective education and industrial relevance.

Numerical Prediction of Solid Particle Erosion in Jet Pumps Based on a Calibrated Model

Jet pumps are widely used in petrochemical processes, nuclear cooling, and wastewater treatment due to their simple structure, high reliability, and stable performance under extreme conditions. However, when transporting solid-laden two-phase flows, they face severe erosion problems, leading to reduced efficiency, malfunctions, or even failure. Therefore, optimizing jet pump performance and extending its service life is crucial. In this study, an experimental platform was established to conduct experiments on wall erosion in jet pumps. The CFD-DEM method was used to simulate the solid–liquid two-phase flow in the jet pump, comparing six erosion models for predicting erosion rates. The Grey Wolf Optimization algorithm was applied to calibrate model coefficients. The results indicate that the Neilson erosion model shows the best consistency with the experimental results. The inlet flow rate significantly influenced the erosion rates, while the flow rate ratio had a smaller effect. The particle concentration exhibited a nonlinear relationship with erosion, with diminishing impact beyond a certain threshold. As the factors varied, the erosion distribution tended to be uniform, but high erosion areas remained locally concentrated, indicating intensified localized erosion.

Abstract 4137009: Treating Elderly Cardiogenic Shock Patients with a Microaxial Flow Pump; Is It DANGERous?

Background: The Danish German Cardiogenic Shock trial (DanGer Shock) recently showed a reduction in all-cause mortality when treating selected patients with ST-segment elevation myocardial infarction (STEMI) and cardiogenic shock with a microaxial flow pump (mAFP). Whether there is an age-related differential survival benefit is unknown. Objective: To assess the influence of age on 180-day all-cause mortality in patients with STEMI and cardiogenic shock randomized in DanGer Shock. Methods: In DanGer Shock (an open-label, international, multicenter trial), 355 adult patients (aged ≥18 years with no upper age limit) with STEMI and cardiogenic shock were included and randomized to a mAFP (Impella CP) plus standard care or standard care alone. Patients were stratified in quartiles according to age, and logistic regression analyses were used to assess mortality according to age quartiles, and to evaluate whether age modified the treatment effect of the mAFP. Results: From lowest to highest quartile, patients’ ages ranged from 31-59, 60-69, 70-76, and 77-92, respectively. There were no differences in blood pressure, lactate level, left ventricular ejection fraction and shock severity across age groups. However, the proportion of females (41%) and the prevalence of hypertension (64%) was higher in patients aged ≥77 years (highest quartile), while more patients aged <60 years (lowest quartile) had been resuscitated before randomization. Mortality increased incrementally from the lowest quartile to the highest (31% vs. 47% vs. 61% vs. 73%, p log-rank <0.001), with an adjusted odds ratio for death at 180 days of 5.50 (95%CI 2.65-11.8, p<0.001) in the highest quartile compared to the lowest. Patients in the three lower quartiles had a lower absolute mortality at 180 days if randomized to the mAFP group, whereas patients in the highest quartile had a higher mortality if randomized to the mAFP group, p=0.028 for interaction, Figure. Conclusion: In patients with STEMI-related cardiogenic shock, the overall mortality increased with advancing age, and treatment benefit of the mAFP appeared to diminish in the eldest patients. (DanGer Shock, NCT01633502)

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Validation through internal flow physics of response surface methodology optimized mixed flow pump as turbine

In order to determine the optimal working efficiency of mixed flow pumps as turbine (MF-PAT) under a design condition of 10m3kw, this study takes the number of blades, blade wrap angle, impeller outer diameter, and impeller inlet width as design variables. Based on the center combination design method, experimental scheme design is carried out, and the head, shaft power, and efficiency of the turbine are used as evaluation indicators. A response surface model is constructed for optimization analysis, and the optimal geometric parameter combination of the impeller for MF-PAT is determined. For MF-PAT with forward-curved blade impeller in this paper, the optimal parameter combination is recommended as blade number Z = 6, blade wrap angle α = 47°, impeller outer diameter D2 = 140 mm and impeller inlet width b2 = 34 mm. The results show that compared with the original scheme, its efficiency has increased by 7.8 %. The established response surface model can reflect the relationship between evaluation indicators and design variables, and can be used for optimizing the geometric parameters of MF-PAT impellers. It can effectively enhance the blade's constraint ability on liquid flow, reduce hydraulic losses, and improve the performance of MF-PAT. Apply the ns-ds methodology for this and future mixed flow optimized pumps as turbines.

Study on cavitation flow and high-speed vortex interference mechanism of high-speed inducer centrifugal pump based on full flow channel

Study on cavitation flow and high-speed vortex interference mechanism of high-speed inducer centrifugal pump based on full flow channel

Nonlinear Control of Photovoltaic (PV) Solar-Powered Centrifugal Pump for Irrigation System: A Case Study of Fadak Farm in Karbala

Abstract In both the agricultural and industrial sectors, pumping water is essential. Due to its arid climate, our Saharan area has a substantial solar energy resource, making constructing a PV solar irrigation system possible. Given solar resources' unpredictable and intermittent nature, it is imperative to set up a system that permits optimal usage. This study aims to design and simulate a solar pumping system's effective nonlinear direct torque command. A solar generator provides an asynchronous three-phase machine coupled to a centrifugal pump as part of the system. MPPT monitors the boost converter via duty cycle. The solar generator's functioning at full power will be ensured. The first uses PSO in the MPPT system to supply the motor pump with three phases of power. The second one employs direct torque command (DTC) to regulate the operation of a centrifugal pump coupled with an induction machine. More advancements will be made to the DTC scenario. The proposed mathematical model of the solar irrigation system was simulated using a MATLAB simulation environment, adopting accurate data provided by Fadak Farm. The maximum power extracted from PV tends to peak at 280 Wp with the assistance of particle swarm optimization that energizes the use of the centrifugal pump for the proposed irrigation system. It is evident from numerical simulation results based on accurate input data that the power extracted from PV solar is positively affected by solar radiation and surface temperature variations. It is clear from simulation results that the speed of three–phase I.M motor converges to 22.5 rad/sec, and water flow pumping by centrifugal is decreased and increased, converging to 7.5 *10-8 m/s with the variation of solar irradiance.

Numerical investigation on the internal flow and wear characteristics of solid–liquid two-phase flow in a centrifugal pump under different stall levels

This paper investigates the flow structures and wear characteristics of solid–liquid two-phase flow in a centrifugal pump under stall conditions using the numerical method. The Computational Fluid Dynamics-Discrete Element Method coupling approach is employed to model the particle–particle and particle–liquid interactions; furthermore, the entropy theory is utilized to evaluate the energy loss and Erosion-Corrosion Research Center model is used to predict wear characteristics. The results indicate that compared to the critical stall condition, deep stall condition leads to a significant increase in the number and size of stall vortices within the impeller channel, which results in a 22% increase in channel blockage and a more uneven particle distribution. The dominant frequency of pressure pulsation in the impeller is the shaft frequency (fn), and the secondary frequency of 0.11 fn is the characteristic frequency of stall vortex. As the stall degree increases, the amplitude of pressure pulsation increases. Turbulent dissipation entropy production and wall entropy production are identified as the primary contribution to energy loss. The majority of energy loss in the centrifugal pump occurs within the impeller and volute, and the entropy production increases proportionally to the stall degree. Wear rate is strongly correlated with the impact frequency, as the stall degree increases, both the impact frequency and wear rate exhibit a gradual decrease.

Experimental and numerical the effect of cavitation detection on hydraulic performance of the centrifugal pump based on different geometrical configurations

The cavitation phenomena and its experimental evaluation of hydraulic pump performance are the subjects of this study. Both qualitative and quantitative assessments of a pump's flow structure were carried out. The unsteady flow in a pump with various impeller geometry characteristics was investigated numerically. In-depth examinations of the local flow parameters for the static pressure, pump head, vapour volume variation fraction, and pressure fluctuations in the time and frequency domains were conducted. The findings showed that the low-pressure region that closed the impeller eye close to the leading edge of the blade is where the cavitation phenomena takes place. Additionally, the results showed that the blade passing frequency (BPF) and the pump's rotational frequency (RF) are two significant dominant frequencies in the device. Furthermore, the numerical results show that modest cavitation occurred at the design mass flow for Z=3, 4, 5, 6, and 7 impeller blades.

Study on the Spatio-temporal Evolutionary Properties of Gas-liquid Two-phase Flow in Centrifugal Pump as Turbine (PAT)

With the increasing complexity of the industrial production process, the transmission medium of the hydraulic turbine is no longer satisfied, and the gas-liquid two-phase mixed medium has to be considered. The presence of gas in the transmission medium will alters the internal flow structure of the hydraulic turbine and affect its operational stability. Therefore, for the purpose of clarifying the influence of inlet gas content on the internal flow of PAT, the unsteady flow of the PAT is simulated in this paper using numerical simulation. Based on the numerical simulation results, the influence of inlet gas content on the internal flow characteristics, characteristics of pressure fluctuation in impeller and volute, and vortex evolution of flow field are analyzed. The accumulation of gas phase leads to the emergence of vortices, and regions with low pressure values appear at the vortex generation. The major factor of the periodic variation of pressure fluctuation between volute and cut-water is the dynamic and static interference of impeller. The increase of gas content causes more flow disorder in the cut-water region and the volute contraction section. Since the gas in the flow channel is predominantly on the suction side of blades, the flow field on the suction side is more complex than that on the pressure side, and the amplitude of pressure fluctuation increases appropriately. The vortex structure is mainly distributed on balance hole, inlet area of impeller and suction side of blade. As the blade rotates, there are new shedding and growth of vortices, and finally attached to the volute wall. Increasing gas content enhances the influence of blade rotation on the vortex evolution characteristics in the volute and impeller.