Characteristics Of Pump Research Articles

Study on the Cavitation Characteristics of Shroud Clearance in Prototype and Model of a Kaplan Turbine

Model tests and model calculations are the most basic means currently available to study the characteristics of the axial-flow pumps and Kaplan turbines in a systematic manner. Large and medium-sized turbine units and axial-flow pumps must rely on model tests and model calculations to ensure the performances of prototype units before designing. The conversions between models and prototypes are mainly carried out through similarity criteria. However, it is difficult to meet all the similarity criteria in the model tests and the similarity conversions, and the hydraulic and cavitation performances of the model and the prototype are often different. In this paper, numerical calculations of shroud clearance cavitation are performed on both the prototype and model using different cavitation coefficients. The results indicate that the prototype and model have a similar clearance cavitation flow regularity when the cavitation coefficient changes, but they have different energy characteristics and cavitation characteristics. In cavitation conditions, the prototype has higher energy characteristics than the model and the critical cavitation coefficient is similar to the model. When the cavitation coefficient is higher than the critical cavitation coefficient, compared to the model, the blade cavitation performance of the prototype is worse, and the clearance cavitation and runner chamber cavitation are more serious. If the cavitation coefficient decreases to the device cavitation coefficient, the runner chamber of the prototype will cavitate, even though the model has not cavitated yet. The comparison of shroud clearance cavitation between the prototype and the model can be used as a reference for the accuracy of similarity conversion results between the model and the prototype. It also has a positive impact on the design and operation of the prototype.

A quasi-analytical prediction method for gear load-independent power losses for shroud approaching

To limit the adverse effect of the fluid pressure field in high-speed gearing systems, especially for the main reducer of helicopters, shrouds usually adopted to enclose and approaches the high-speed gears will play a vital role in the windage and pumping power losses in axial and radial directions. To better explore and predict the total load-independent losses, this paper proposes an improved quasi-analytical method to quantify the power losses caused by the windage and pumping effects, considering the gear pump characteristics with the compressibility of the air or air-oil mixture. The theoretical calculations using the improved model are then compared with experimental results in the open literature. Leveraging the swept volume of the gear pump, the squeezing/pocketing behavior of the fluids in the tooth space can get a better understanding as the shroud approaches the gear pair.

Effects of biventricular shunt on pump characteristics in a maglev total artificial heart.

Severe left ventricular failure can progress to right ventricular failure, necessitating alternatives to heart transplantation, such as total artificial heart (TAH) treatment. Conventional TAHs encounter challenges associated with miniaturization and hemocompatibility owing to their reliance on mechanical valves and bearings. A magnetically levitated TAH (IB-Heart) was developed, utilizing a magnetic bearing. The IB-Heart features a distinctive biventricular shunt channel situated between the flow paths of the left and right centrifugal blood pumps, simplifying and miniaturizing its control system. However, the impact of these shunt channels remains underexplored. This study aimed to investigate the effects of shunt flow on pump characteristics and assess the IB-Heart's potential to regulate flow balance between systemic and pulmonary circulation. At a rotational speed of 2000 rpm and flow rate range of 0-10 L/min, shunt flow exhibited a minor impact, with a 1.4 mmHg (1.3%) effect on pump characteristics. Shunt flow variation of about 0.13 L/min correlated with a 10 mmHg pressure difference between the pumps' afterload and preload conditions. This variance was linked to changes in the inlet flow rates of the left and right pumps, signifying the ventricular shunt structure's capacity to mirror the function of an atrial shunt in alleviating pulmonary congestion. The IB-Heart's ventricular shunt structure enables passive regulation of left-right flow balance. The findings establish a fundamental technical groundwork for the development of IB-Hearts and TAHs with similar shunt structures. The innovative coupling of centrifugal pumps and the resultant effects on flow dynamics contribute to the advancement of TAH technology.

Numerical Simulation Study on Flow Characteristics of Multistage Centrifugal Pumps under Different Inlet Gas Void Fractions

The flow characteristics of multistage centrifugal pumps in transporting gas–liquid mixed media are highly complex; particularly, the unstable flow of the passage at high gas contents exacerbates energy losses, leading to a decrease in pump efficiency and stability. The excess energy loss in the pump is not conducive to the concept of sustainable development. In this study, a numerical simulation of multistage centrifugal pumps was conducted based on the Euler–Euler heterogeneous two-fluid model. This research revealed that gas primarily accumulates on the suction side of each impeller stage, and the gas distribution decreases progressively with each stage. As the interstage gas volume fraction (IGVF) increases, the gas accumulation within the pump becomes more pronounced. The gas volume fraction of each component is negatively correlated with the flow rate, and the change is more obvious in the impeller. The turbulent kinetic energy distribution inside the impeller is positively correlated with the gas distribution. There is a large fluctuation at 0.6Q and 0.8Q, and the distribution of the impeller vortex is asymmetric. However, the impeller has a lower turbulent kinetic energy near 1.2Q, which indicates that the emergence of gas in the medium increases the high-efficiency area of the multistage pump to a certain extent. This paper reveals how the gas phase is distributed, how energy is lost in the multistage pump, and the gas–liquid two-phase flow characteristics in the pump, which have certain guiding significance for the design and working-condition adjustments of the gas–liquid mixed pump.

Study on Unsteady Flow Characteristics of Cooling Water Pump for Nuclear Power Plant Equipment under Low Flow Rate Conditions

During the operation of cooling water pumps, it is necessary to operate them under conditions of low flow rate. In order to improve the unstable performance of the cooling water pump under low flow rate conditions. Taking the cooling water pump as the research object, the internal flow and pressure pulsation characteristics of the cooling water pump under 0.4Q to 0.6Q conditions were investigated, and the influence of different operating conditions on the performance and vibration of the cooling water pump was analyzed. The ANSYS CFX 2022 software and the SST k-ω turbulence model were used to perform a three-dimensional numerical simulation of the cooling water pump. After analyzing the simulation results, the velocity and pressure cloud and streamline diagram within the semi-spiral suction casing and impeller were obtained. The internal flow state of the cooling water pump was then analyzed in detail under low flow rate conditions. At the same time, a series of monitoring points were set up within the impeller, and the pressure pulsation within the impeller was analyzed using the frequency domain diagram and the radial force polar coordinate diagram. The results show that at flow rates between 0.4Q and 0.6Q, a certain amount of vortex has been generated in the suction casing, which affects the flow state when entering the impeller. Furthermore, significant vortices have been generated in the middle and back part of the blade and mainly concentrated in the pump cover of the mid-open pump. At the same time, when in low flow rate conditions, the primary frequency of pressure pulsation is mainly the axial frequency, with three times the axial frequency and blade frequency following. The amplitude of the pressure surface (PS) of the blade is greater than that of the suction surface (SS) and increases as the flow rate decreases. The internal radial force corresponds with the result of pressure pulsation and exhibits a certain pattern. This study outlines the coolant pump’s internal flow and pressure pulsation characteristics under low-flow conditions. It proposes a solution to stabilize the cooling water pump at low flow rates and provides theoretical guidance for optimizing its design.

Effect of inlet/outlet height difference on P-Q characteristics of an electromagnetic pump for heavy liquid metals

A permanent magnet based electromagnetic pump (EMP) has been designed and fabricated for high temperature heavy liquid metals. It has features of being bi-directional in operation and non-intrusive in technique. The EMP has been characterized by generating its pressure developed vs flowrate (P-Q) curve in a high temperature experimental set up. Usually, the pressure developed by the pump is measured by taking the difference of pressure at discharge and suction ends. In contrast our experiment shows that the measured pressure difference between the suction and discharge end is different from that of the actual pressure developed by the pump. This may be due to the existing height difference between the suction and discharge end of the pump. A systematic study has been performed to analyse the effect of gravity on P-Q curve of such pumps. A method has been proposed to accurately generate the P-Q curve for such pumps for heavy liquid metals. The generated P-Q curve has been compared with available analytical expressions and found to match well with Hvasta et al.

A study on the thermal aging characteristics of an electro-osmotic pump using a liquid crystal polymer as a packaging material

A study on the thermal aging characteristics of an electro-osmotic pump using a liquid crystal polymer as a packaging material

Can pretrained networks be used in fault diagnosis of monoblock centrifugal pump?

Monoblock centrifugal pumps are used daily and play an essential role in agriculture, wastewater treatment, food, paper, gas and oil industries. Extended and endless use of monoblock centrifugal pump can affect the desired pump characteristics, compromising the efficiency of the pump. The condition of a pump is judged based on the high vibration, unusual noise, leakage, etc. Maintaining pump health is essential to increase the productivity in industry. Countless experiments were carried out by researchers to maintain the efficiency of the pump. The main shortcomings of traditional fault diagnosis are the need for a high degree of human intellect and professional knowledge. Such drawbacks have made the researchers provide autonomous and intelligent diagnostic tools. The objective of this article is to investigate the possibility of use of deep learning technique to identify the type of fault present in the monoblock centrifugal pump. First, vibration signals from the monoblock centrifugal pump were acquired and plotted as images that serve as an input for deep learning (DL) algorithms. The deep learning system can analyse the status of the monoblock centrifugal pump and learn from the vibration signal plots. In this paper, pre-trained networks such as ResNet-50, AlexNet, GoogleNet and VGG-16 were used to diagnose the fault in the monoblock centrifugal pump. The outcome of the hyperparameters namely learning rate (LR), batch size (BS), split ratio (SR) and solver were considered and the best performing network was recommended for the monoblock centrifugal pump fault diagnostics. Findings: A higher classification accuracy of 100% with lower training time of 177 s was obtained while using ResNet-50.

Numerical investigation of particle effect on wear characteristic of centrifugal slurry pump based on CFD-DEM coupling

PurposeIn the process of conveying the solid–liquid two-phase medium of the centrifugal slurry pump, the wear of the flow-passing parts is an important problem affecting its life and safe operation. Therefore, a numerical investigation on the wear characteristics of the centrifugal slurry pump under different particle conditions was conducted.Design/methodology/approachA solid-liquid two-phase model based on CFD-DEM coupling is established and used to analyze the flow field and the wear characteristics of the flow-passing parts with different particle densities, volume fractions and sizes.FindingsParticle conditions will affect the pump flow field. To analyze the pump wear characteristics, the wear distribution, wear value and cumulative force laws of flow-passing parts under different particle conditions are obtained. In each flow-passing part, with the increase of particle density, volume fraction and size, the wear area is concentrated and the wear depth increases. Under different particle conditions, the wear is mainly on the volute chamber and the blade pressure surface, and the tangential cumulative force of flow-passing parts is much larger than the normal cumulative force.Originality/valueAn accurate model and a coupled simulation method for predicting the wear of the slurry pump are obtained, and the wear characteristic law can provide a reference for the design of the slurry pump to reduce friction.

Research on the Performance Characteristics and Unsteady Flow Mechanism of a Centrifugal Pump under Pitch Motion

Pitch motion is the key factor affecting the performance characteristics of centrifugal pumps on board ships and exacerbates hydraulic excitation to induce the unsteady vibration of pump units. A hydraulic test platform with swing motion is established to explore the effects of pitch motion on a pump’s performance characteristics. An obvious hump zone exists in the head characteristic curve in the low-flow-rate condition due to the pitch motion. The pump head in the shut-off condition has a significant decrease due to the pitch motion, compared to the static state. The head decrease gradually increases as the maximum pitch angle increases or the pitch period shortens. Specifically, the head in the rated flow condition decreases by 6.3 % to reach a minimum at the maximum pitch angle of 20 degrees in a period of 5 s. Based on a multiple-reference coordinate system, a large eddy simulation with a shear-modified eddy viscosity model is employed to simulate inner flow characteristics under the influence of pitch motion. A distinct vortex flow appears near the blade suction surface and becomes increasingly turbulent as the pitch period shortens. The pitch motion intensifies the unsteady stretching and deformation of vortices. The periodic variations in fluid-induced pressure over time present parabolic features, and the amplitude in the frequency domain reaches its maximum value within a pitch period of 5 s.

Influence of Rotation Speed and Gas Content on the Transient Gas–Liquid Two-Phase Flow of an Electric Submersible Pump

In order to study the internal flow characteristics of the electric submersible pump (ESP) when the gas–liquid two-phase flow is conveyed by the variable frequency variable speed operation and the change of the imported gas content, the impeller of the Q10# ESP is taken as the research object, based on the Eulerian-Eulerian non-homogeneous phase. The flow model, the unsteady Reynolds time-averaged N-S equation, and the standard k-ε turbulence model are used for transient simulation calculations of the gas–liquid two-phase flow in the impeller of the ESP. Calculations show that with the rotation of the impeller, the gas phase is unevenly distributed in the flow channel. The gas phase is mainly concentrated on the inlet side of the flow channel near the front cover, and the gas phase exhibits periodic aggregation and diffusion in the flow channel. When the impeller speed increases, the period of periodic accumulation and diffusion of gas in the flow channel is shortened and the gas concentration in the impeller decreases, the overall flow velocity in the flow channel increases, and the pressure difference between the inlet and outlet increases. The pressure difference between the two sides of the blade is proportional to the speed of the impeller, and the fluctuation frequency of the blade surface also increases. As the gas content increases, the maximum concentration of gas phase in the flow channel increases. The area occupied by the high concentration of gas phase in the flow channel expands toward the blade’s working surface, and periodically accumulates, diffuses, and grows. The gas-liquid splitting area shrinks toward the front cover side and the pump. The internal pressure increases slightly, the main flow velocity increases, and the vortex action range increases.

Electromagnetic force investigation of electromagnets with variable pole area in an electromagnetic diaphragm pump.

Electromagnetic diaphragm pump is a kind of widely applied diaphragm pump that has promising sealing performance, simple structure and low power loss. Planar pole electromagnet is a significant component of the electromagnetic diaphragm pump. However, the sharply changing displacement-force characteristics of the planar pole electromagnet do not match the constant load characteristics of the electromagnetic diaphragm pump. Herein, an electromagnet with variable pole area is put forward. A theoretical relationship between structural parameters, the Ampere turns and the electromagnetic force of the electromagnet with variable pole area is determined by analyzing the equivalent magnetic circuit of the electromagnet with variable pole area. The experimental results imply that the initial electromagnetic force of the electromagnet with variable pole area is 32.51% larger than the planar pole electromagnet, the engaging electromagnetic force of the electromagnet with variable pole area is 22.3% smaller than the planar pole electromagnet and the displacement-force characteristics of the electromagnet with variable pole area match the constant load characteristics of the electromagnetic diaphragm pump.

Transient Hydrodynamic Characteristics of a High-Speed Axial Flow Water-Jet Pump during Variable Speed Process

To investigate the transient characteristics of high-speed axial flow water-jet pumps during start-up and emergency acceleration as well as to analyze how different accelerations affect the performance of internal flow, the k–ω turbulence model of the SST model and Zwart cavitation model were used to perform unsteady simulation on an impeller rotating at a speed of 1850. The steady-state numerical simulation method was verified by the experimental data, the numerical calculation results were basically consistent with the experimental data, the margin of error was within 5%, and the numerical simulation method was reliable. The results show that there was an obvious transient effect in the process of variable speed, and the thrust reached a stable state later than the speed. The buffer times for start-up times of 1 s, 2 s, and 3 s were 0.0394 s, 0.0375 s, and 0.0282 s, respectively, and the buffer times for the acceleration times of 0.5 s, 1.0 s, and 1.5 s were 0.0330 s, 0.0273 s, and 0.0230 s, respectively. The greater the acceleration, the more serious the flow rate and thrust lag behind the speed, and the greater the impact thrust. Under the same acceleration, the buffer time required in the start-up process was 19.3~22.6% longer than that in the acceleration process. During the change in speed of the high-speed water-jet pump, the vortex core area of the suction surface (SS) first appeared on the side of the shroud at the inlet, increased with the increase in the rotational speed, and developed toward the middle of the impeller. However, after the flow was stabilized, the vortex core region gradually shrank and eventually disappeared. When the rotational speed reached 0.6 times the design speed, cavitation occurred at the leading edge (LE) of the blade, and the cavitation area increased with the increase in the rotational speed. When reaching the same speed, the greater the acceleration, the more serious the cavitation. Under the design speed, that is, 6000 r/min, the cavitation volume fraction of the 1 s start-up process was 7.32%, the 2 s start-up process was 5.84%, the 3 s start-up process was 5.32%, and the 0.5 s acceleration process was 6.86%. The cavitation volume fraction of the 1 s acceleration process was 5.04%, and that of the 1.5 s acceleration process was 4.23%. Under the same acceleration, the cavitation volume fraction of the start-up process was 6.7~25% larger than that of the acceleration process. Compared with the start-up process and acceleration process under the same acceleration, the accelerated process had a smaller region of vortex core, stronger anti-cavitation ability, and more stable flow than the start-up process. During the actual operation process of the water-jet pump, it is advisable to use smaller accelerations and segmented accelerations as much as possible until the design speed is reached. The research findings serve as a foundation for future investigations into the transient characteristics of high-speed water-jet pumps operating under variable speed conditions.

Analyses of energy loss characteristics of a low-specific speed centrifugal pump as turbines (PATs) based on entropy generation analysis model

Analyses of energy loss characteristics of a low-specific speed centrifugal pump as turbines (PATs) based on entropy generation analysis model

CHARACTERISTICS OF CENTRIFUGAL PUMP FOR PUMPING BINGHAM LIQUID WITH DIFFERENT VALUES OF YIELD STRESSES

General techniques for designing centrifugal pumps are based on calculation features and experimental data on water pumping. On the other hand, pumping non-Newtonian liquids, and Bingham liquids in particular, can change the position of the best efficiency points and change the characteristics. The use of numerical methods allows not only to speed up the search for optimal flow parts, but also to check the possibility of pump operation under extreme operating parameters with different viscosities of a non-Newtonian liquid: from zero viscosity (ideal liquid) to extremely high values, and to create more universal design methods pumps of various types. General techniques for designing centrifugal pumps for pumping non- Newtonian fluids involve adjusting the characteristic depending on the effective viscosity, which for Bingham fluid is calculated from the plastic viscosity. The paper determines the influence of the values of the yield stresses of the Bingham fluid on the characteristics of the centrifugal pump by solving the Reynolds equations, continuity, the turbulence model and the rheological model of the Bingham fluid. It was found that with the same flow rate, the pressure at the pump outlet decreases by no more than 5,1 %. There is a slight shift in the characteristic to the zone of lower flow rate. Thus, the yield stresses have practically no effect on the pressure characteristic of the centrifugal pump. The yield stresses have a sufficient influence on the pump efficiency that they must be considered during the design of the flow part. The efficiency decreases by 10 % when pumping liquid with yield stresses of 100 Pa. A decrease in the efficiency of the pump may be related to the kinematic parameters of the pump and the result of a decrease in pressure distribution on the blade.

Investigation of cavitation and flow characteristics of tip clearance of bidirectional axial flow pump with different clearances

With the increasing application of bidirectional axial pump, it is necessary to study the flow and cavitation characteristics of bidirectional pump. In this paper, the cavitation and flow characteristics of the tip clearance under different clearances and different cavitation numbers of the S-hydrofoil bidirectional axial flow pump were studied by combining experimental and numerical simulation methods under reverse operation conditions. The section of the bidirectional pump was experimentally studied by high-speed photography and pressure pulsation. Based on the method of RANS, the SST-CC turbulence model and ZGB cavitation model were used to simulate the clearance cavitation of the bidirectional pump, and the cavitation morphology, velocity distribution, clearance vortex structure and energy distribution of blade tip clearance were investigated. The study reveals the flow characteristics of the clearance flow field of the bidirectional pump, and provides reference for the design and operation of it.

Magnetohydrodynamic Analyses of a Miniature, Dual-Stage Electromagnetic Pump for Lead and Sodium In-Pile Test Loops

To support the development of Generation IV nuclear reactors, in-pile and out-of-pile test loops with miniature, submersible Direct-Current Electromagnetic Pumps (DC-EMPs) are used to investigate compatibility and corrosion issues of nuclear fuel and structure materials with flowing molten lead and alkali liquid metals. Owing to the absence of detailed experimental measurements and because of its simplicity and low computational cost, the Equivalent Circuit Model (ECM) is widely used to predict the pump characteristics. The simplifying assumptions in the ECM contribute to overpredicting the pump characteristics by >10%. To gain insight into the pump operation and assess the effect of various assumptions in ECM, not possible even experimentally, this work performed three-dimensional (3-D), Magneto-Hydro-Dynamic (MHD) analyses of a 66.8-mm-diameter, submersible, dual-stage DC-EMP, recently developed by the authors, for circulating molten Pb and liquid Na at up to 500°C. The solution of the coupled electromagnetism equations and the momentum and energy balance equations calculates the pump characteristics and provides 3-D images of the flow, electric current, and magnetic field strength distributions in the flow duct. The Grid Convergence Index (GCI) criterion confirmed the adequacy of the employed numerical mesh refinement and the results conversion. Results demonstrate strong dependence of the magnetic field strength distribution in the flow duct on the value and the distribution of the electric current but negligible effects of the fluid temperature on joule heating and pump characteristics. The Lorentz force highest densities occur at the entrance of the two pumping stages, and approximately 10.0% of the total force occurs in the fringe regions upstream and downstream of pumping stages. The MHD pump characteristics are in general agreement with, but consistently lower than, the ECM predictions. For molten lead and liquid sodium, the difference between the calculated characteristics increases with increased flow rate and input current, up to 12% and 14%, respectively.

Effect of variable speed conditions on the internal flow characteristics of a multiphase pump

The multiphase pump is an important device in the mixing and transmission technology for oil and gas. It simplifies the entire process of oil and gas extraction and transmission. In actual engineering, the gas volume fraction (GVF) of the fluid being transported is constantly changing, and this change has an important impact on the internal flow characteristics of the pump. The multiphase pump also needs to change the operating speed to adapt to this change to keep its internal flow field and external characteristics in a good operating range. In this work, the internal flow characteristics of the pump unit under different velocity conditions for the bullet flow type are compared and analyzed. It can be concluded that the higher the rotational speed, the better the pressure increment performance. The lower efficiency of the multiphase pump under high-speed conditions is mainly caused by the increase in the velocity difference between gas and liquid phases in the back area of the guide vane outlet, which leads to an increase in a vortex. Unlike the design point condition, the efficiency curves of the two high-speed conditions show an increasing trend in the design flow interval from 0.1 times to 1.2 times. It shows that an increase in speed causes the high-efficiency zone of the multiphase pump to shift to the high-flow rate zone. Finally, an experimental investigation of the variable velocity condition was performed to verify the validity of the numerical simulation.

Experimental study on operating characteristics and control strategy of CO2 heat pump in circulating heating mode

The CO2 heat pump is a promising low carbon technology for domestic hot water production due to its potential heating advantages and the natural properties of CO2. However, the change pattern of operational parameters, heating time, and energy efficiency of CO2 heat pump in circulating heating mode remains to be fully revealed. Meanwhile, the matching control strategies to improve the system performance have not been developed. Firstly, we experimentally revealed the operating characteristics of CO2 heat pump in circulating heating mode. Results demonstrated that it is quite challenging to simultaneously maintain the lower input power, shorter heating time, and higher coefficient of performance (COP) without taking control measures. It is found that the circulating heating process could be divided into stable and upward periods, depending on the water temperature at the inlet of gas cooler. The deterioration of the system performance appears during the upward period, where the instantaneous COP drops from 4.1 to 3.1. This is because input power rises, while the heating capacity drops as the water temperature at the inlet of gas cooler increases. Secondly, we experimentally developed a matching control strategy to improve the system performance during the upward period. The control method is the correlation of optimal electronic expansion valve opening, and the regulation frequency is regulating for 1 °C per rise of the water temperature at the inlet of gas cooler. As a result, the overall COP increased by 3.71%, and the overall input power reduced by 3.74% while the heating time remained constant.

A selection method of variable speed centrifugal pumps for maximum hydraulic efficiency

Variable speed pumps (VSPs) are more energy efficient compared to other flow control methods such as throttling control valves. However, their selection process is not straightforward because the pump characteristics should be optimised against the load profile of the flow system for maximum hydraulic efficiency. This paper presents a VSPs selection method based on generic mathematical models of centrifugal pumps efficiency, characteristics and similitude, which enables the extension of this method to other types of turbomachines. This selection method results in a nonlinear algebraic equation that is solved numerically to obtain a reference flow rate that maximises the pumping system hydraulic efficiency. This reference flow rate is subsequently used to obtain the pump characteristic curves at all operating pump speeds. The results show that this method is fast, accurate and reliable. Because the developed method uses generic pump models rather than specific models from manufacturers’ databases, it enables the integration of VSP selection process in early engineering design phases of pumping systems.