In order to investigate the self-priming process of the self-priming pump,an unsteady simulation was conducted where the Navier-Stokes equations were used with the Lagrangian-Eularian mo-del.In course of this investig...In order to investigate the self-priming process of the self-priming pump,an unsteady simulation was conducted where the Navier-Stokes equations were used with the Lagrangian-Eularian mo-del.In course of this investigation,the volume fractions,pressure distribution and self-priming time were carried out.By analyzing the volume,velocity and pressure distribution of the gas-liquid two-phase flow at different time,the two-phase content via the variation law of the two-phase flow in the pump was carried out.By monitoring and analyzing the gas-liquid flow at the outlet of the pump,the self-priming time and crucial periods were given.Two phenomena were mainly characterized by the self-priming process such as the gas-liquid mixing and separation,which occur in the early stage of self-priming process.During that period the gas-liquid mixing clouds appear on the outer edge of the impeller,and the instantaneous void fraction at the inlet and outlet of the impeller decreases obviously.It was also established from the transient study that the gas has a major influence on the hydraulic performance of the pump at the early stage of operation.To increase the usage of self-priming pump and to also understand the energy conversion of the pump,it is very essential to investigate and establish the basic working principle of the self-priming pump.展开更多
A self-priming pump is a centrifugal pump that has the ability to prime itself. Typically, its performance dependson the configuration of its reflux hole. In this study, the ANSYS FLUENT software is used to investigat...A self-priming pump is a centrifugal pump that has the ability to prime itself. Typically, its performance dependson the configuration of its reflux hole. In this study, the ANSYS FLUENT software is used to investigate the effectsof three different radial positions of the reflux hole on gas-liquid two-phase distribution, pressure pulsation, andimp during self-priming. The research results indicate that: (1) The effective channel size for the reflux liquid toenter the volute varies depending on the location of the reflux hole. The effect of the impeller rotation on thereflux liquid becomes more obvious as the setting distance of the reflux aperture decreases. (2) The position ofthe reflux hole significantly affects the gas phase mass fraction inside the impeller, resulting in a significant reductionin the time it takes for the mass fraction to exceed 80%. (3) The position of the reflux hole significantly affectsthe average pressure on each monitoring surface. (4) Placing the reflux hole at a excessively distant radial distancecan result in an excessive vertical component. (5) The self-priming performance of the pump can be improved tosome extent by placing the return hole at a small radial distance.展开更多
Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure throug...Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.展开更多
During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforatio...During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforation as a cavitation-mitigation strategy,in this study several mixed-flow pump models incorporating perforations were developed.Numerical simulations were performed for configurations with circular holes positioned at different locations along the blade leading edge,and the computational results were validated against experimental measurements.The findings indicate that the location of the perforations plays a decisive role in cavitation suppression.Moving from the blade rim toward the hub along the leading edge,the critical net positive suction head,NPSH_(cr),initially decreases and subsequently increases,while remaining consistently lower than that of the reference non-perforated configuration.The perforations promote the transfer of high-pressure fluid from the pressure side to the suction side of the blade,thereby alleviating local low-pressure regions.This pressure compensation significantly reduces the extent of low-pressure zones in the vicinity of the perforations,leading to a marked suppression of cavitation both locally and downstream of the perforated regions.展开更多
Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and rene...Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and renewable energy sources while considering operational constraints of existing systems.This study investigates a hybrid heating system combining a natural gas boiler(NGB)with an air-to-water heat pump(AWHP),evaluated through a combination of laboratory experiments and dynamic modelling.A prototype developed in the Electrical and Energy Engineering Laboratory enabled the characterization of both heat generators,the collection of experimental data,and the calibration of a MATLAB/Simulink model,including emissions and exhaust analyses.Sensitivity analyses were performed to identify optimal configurations for energy efficiency and system control,accounting for interactions between subsystems.Results highlight that hybridisation significantly improves primary energy efficiency and reduces fuel consumption compared to conventional NGB-only systems.Environmental performance,assessed through CO_(2) and NOx emissions and renewable energy integration,demonstrates the benefits of partial electrification in the residential sector.Economic assessment further quantifies decarbonization costs and fuel savings,illustrating tradeoffs between low-capital,moderate-performance systems and high-efficiency,high-renewable solutions requiring larger investments.The analysis shows that strategic decisions for residential decarbonisation cannot be separated from system-wide considerations,including control strategies,component integration,and economic feasibility.The study underlines the importance of hybrid and renewable-based solutions as pivotal pathways for energy transition in the residential building sector.展开更多
To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-ge...To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.展开更多
The self-priming process of a pump involves a complex gas-liquid two-phase flow.Studying the distribution of gas and water and the evolution of their flow in the pump is of great importance to optimize this process an...The self-priming process of a pump involves a complex gas-liquid two-phase flow.Studying the distribution of gas and water and the evolution of their flow in the pump is of great importance to optimize this process and shorten the pump self-priming time.In the present study,a standard k-εturbulence model and a multiphase flow model have been used to simulate the self-priming pump process considering four different reflux hole areas.A comparison of the distribution of air and water distribution on the axial surface and inside the volume have been carried out for the different considered cases.The pattern formed by the streamlines at different times during the whole self-priming process has also been investigated.The results show that the velocity at the trailing edge of the impeller outlet is the largest.The flow in the pump cavity is.complicated by the formation of vortices.The number,shape and location of the vortices change depending on the considered configuration.展开更多
Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluct...Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.展开更多
Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibra...Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.展开更多
In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,t...In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.展开更多
Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,i...Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.展开更多
Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribu...Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribution network emergency recovery framework.A phase-space reconstruction and stacked integrated model for predicting wind and photovoltaic generation during typhoon disasters is proposed in the first stage.This provides guidance for second-stage post-disaster emergency recovery scheduling.The emergency recovery scheduling model is established in the second stage,and this model is supported by a thermal power-generating unit,mobile emergency generators,and distributed generators.Distributed generation includes wind power generation,photovoltaics,fuel cells,etc.Simultaneously,we con-sider the gray-start based on the pumped storage unit to be an important first step in the emergency recovery strategy.This model is val-idated on the improved IEEE 33 node system,which utilizes data from the 2022 super typhoon“Muifa”in Zhoushan,Zhejiang,China.Simulations indicate the superiority of a gray start with a pumped storage unit and the proposed emergency recovery strategy.展开更多
BACKGROUND Proton pump inhibitors(PPIs)are widely used,including among cancer patients,to manage gastroesophageal reflux and other gastric acid-related disorders.Recent evidence suggests associations between long-term...BACKGROUND Proton pump inhibitors(PPIs)are widely used,including among cancer patients,to manage gastroesophageal reflux and other gastric acid-related disorders.Recent evidence suggests associations between long-term PPI use and higher risks for various adverse health outcomes,including greater mortality.AIM To investigate the association between PPI use and all-cause mortality among cancer patients by a comprehensive analysis after adjustment for various confounders and a robust methodological approach to minimize bias.METHODS This retrospective cohort study used data from the TriNetX research network,with electronic health records from multiple healthcare organizations.The study employed a new-user,active comparator design,which compared newly treated PPI users with non-users and newly treated histamine2 receptor antagonists(H2RA)users among adult cancer patients.Newly prescribed PPIs(esomeprazole,lansoprazole,omeprazole,pantoprazole,or rabeprazole)users were compared to non-users or newly prescribed H2RAs(cimetidine,famotidine,nizatidine,or ranitidine)users.The primary outcome was all-cause mortality.Each patient in the main group was matched to a patient in the control group using 1:1 propensity score matching to reduce confounding effects.Multivariable Cox regression models were used to estimate hazard ratios(HRs)and 95% confidence interval(CI).RESULTS During the follow-up period(median 5.4±1.8 years for PPI users and 6.5±1.0 years for non-users),PPI users demonstrated a higher all-cause mortality rate than non-users after 1 year,2 years,and at the end of follow up(HRs:2.34-2.72).Compared with H2RA users,PPI users demonstrated a higher rate of all-cause mortality HR:1.51(95%CI:1.41-1.69).Similar results were observed across sensitivity analyses by excluding deaths from the first 9 months and 1-year post-exposure,confirming the robustness of these findings.In a sensitivity analysis,we analyzed all-cause mortality outcomes between former PPI users and individuals who have never used PPIs,providing insights into the long-term effects of past PPI use.In addition,at 1-year follow-up,the analysis revealed a significant difference in mortality rates between former PPI users and non-users(HR:1.84;95%CI:1.82-1.96).CONCLUSION PPI use among cancer patients was associated with a higher risk of all-cause mortality compared to non-users or H2RA users.These findings emphasize the need for cautious use of PPIs in cancer patients and suggest that alternative treatments should be considered when clinically feasible.However,further studies are needed to corroborate our findings,given the significant adverse outcomes in cancer patients.展开更多
We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening...We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.展开更多
The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this stud...The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this study is to carry out a comparative analysis of two dewatering pumping systems (Solar Kit and GMP) for water mobilization on a certain number of criteria such as sustainable use, economic aspect and performance. To achieve this, the adapted methodology consisted first of all in the development of a data collection tool in the field. Then flow measurements, estimation of fuel consumption, pressure height, etc., were carried out. Thus, the data collection involved a sample of 120 irrigators who had to use the two (2) types of pumping systems. The collected data were analyzed and processed with appropriate software. The results of the study show that the two pumping systems studied have strengths and constraints. Thus, the solar pumping system has a significant investment cost, very low maintenance and a low operating cost. On the other hand, the system with a generator has a relatively low investment cost (25 to 30 times less than solar), but a relatively high operating, upkeep and maintenance cost. He adds that these assets and constraints must be taken into consideration when an investment is made. This study shows that 74% of producers use GMP compared to 26% who use the Solar Kit. But in practice, the Solar Kit is more reliable for producers from the point of view of planted area, environmental management and investment costs, supply of fuel and lubricant. These results indicate better performance of the solar pumping system compared to GMP at the study sites.展开更多
Jet pumps often suffer from efficiency losses due to the intense mixing of power and suction fluids,which leads to significant kinetic energy dissipation.Enhancing the efficiency of such pumps requires careful optimiz...Jet pumps often suffer from efficiency losses due to the intense mixing of power and suction fluids,which leads to significant kinetic energy dissipation.Enhancing the efficiency of such pumps requires careful optimization of their structural parameters.In this study,a computational fluid dynamics(CFD)model of a hydraulic jet sand-flushing pump is developed to investigate the effects of throat-to-nozzle distance,area ratio,and throat length on the pump’s sand-carrying performance.An orthogonal experimental design is employed to optimize the structural parameters,while the influence of sand characteristics on pumping performance is systematically evaluated.Complementary indoor experiments are used to validate the numerical results,yielding an optimized configuration with a throat-to-nozzle cross-sectional area ratio of 4,a throat length five times the throat diameter,and a throat-to-nozzle distance equal to the nozzle diameter.Under a power fluid flow rate of 1.7 m3/h with this area ratio,the sand-carrying efficiency reaches its peak,achieving a sand transport rate of 290 g/min(6.7 L/h).Comparison of CFD predictions with experimental data across different area ratios demonstrates excellent agreement,with an average relative error of 2.44%and an average absolute error of 3.56%,confirming the reliability of the simulation approach.展开更多
Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the ...Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the normal energy exchange processes within the pump.Therefore,effective monitoring of cavitation in centrifugal pumps is crucial.This article presents a study that approaches the issue from an acoustic perspective,using experimental methods to gather and analyze acoustic data at the inlet and outlet of centrifugal pumps across various flow rates,with hydrophones as the primary measuring instruments.Results show that flow rate significantly affects noise levels in both non-cavitation and mild cavitation stages,with noise increasing as the flow rate rises.As the cavitation margin(NPSHa)decreases,inlet and outlet noise trends diverge:inlet noise drops sharply,while outlet noise initially increases before sharply decreasing.Both exhibit a distinct zone of abrupt change,where NPSHa values offer earlier cavitation detection than traditional methods.The noise at the pump’s inlet and outlet primarily consists of discrete and broadband noise,with most energy concentrated at discrete frequencies—shaft frequency(24 Hz),blade frequency(144 Hz),and their harmonics.As NPSHa decreases,the inlet’s discrete and broadband noise frequencies decline,while they increase at the outlet.Monitoring changes in these spectrum characteristics provides an additional means of predicting cavitation onset.展开更多
Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high ef...Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high efficiency and reliability.However,the ambiguity surrounding the output flow characteristics of individual two-dimensional pumps poses a significant challenge in achieving precise closed-loop control of the EHA positions.To address this issue,this study established a comprehensive numerical model that included gap leakage to analyze the impact of leakage on the output flow characteristics of a two-dimensional piston pump.The validity of the numerical analysis was indirectly confirmed through meticulous measurements of the leakage and volumetric efficiency,ensuring robust results.The research findings indicated that,at lower pump speeds,leakage significantly affected the output flow rate,leading to potential inefficiencies in the system.Conversely,at higher rotational speeds,the impact of leakage was less pronounced,implying that the influence of leakage on the pump outlet flow must be carefully considered and managed for EHAs to perform position servo control.Additionally,the research demonstrates that two-dimensional motion does not have a unique or additional effect on pump leakage,thus simplifying the design considerations.Finally,the study concluded that maintaining an oil-filled leakage environment is beneficial because it helps reduce the impact of leakage and enhances the overall volumetric efficiency of the pump system.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.51879120)。
文摘In order to investigate the self-priming process of the self-priming pump,an unsteady simulation was conducted where the Navier-Stokes equations were used with the Lagrangian-Eularian mo-del.In course of this investigation,the volume fractions,pressure distribution and self-priming time were carried out.By analyzing the volume,velocity and pressure distribution of the gas-liquid two-phase flow at different time,the two-phase content via the variation law of the two-phase flow in the pump was carried out.By monitoring and analyzing the gas-liquid flow at the outlet of the pump,the self-priming time and crucial periods were given.Two phenomena were mainly characterized by the self-priming process such as the gas-liquid mixing and separation,which occur in the early stage of self-priming process.During that period the gas-liquid mixing clouds appear on the outer edge of the impeller,and the instantaneous void fraction at the inlet and outlet of the impeller decreases obviously.It was also established from the transient study that the gas has a major influence on the hydraulic performance of the pump at the early stage of operation.To increase the usage of self-priming pump and to also understand the energy conversion of the pump,it is very essential to investigate and establish the basic working principle of the self-priming pump.
基金the National Natural Science Foundation of China(Research Project No.52169018).
文摘A self-priming pump is a centrifugal pump that has the ability to prime itself. Typically, its performance dependson the configuration of its reflux hole. In this study, the ANSYS FLUENT software is used to investigate the effectsof three different radial positions of the reflux hole on gas-liquid two-phase distribution, pressure pulsation, andimp during self-priming. The research results indicate that: (1) The effective channel size for the reflux liquid toenter the volute varies depending on the location of the reflux hole. The effect of the impeller rotation on thereflux liquid becomes more obvious as the setting distance of the reflux aperture decreases. (2) The position ofthe reflux hole significantly affects the gas phase mass fraction inside the impeller, resulting in a significant reductionin the time it takes for the mass fraction to exceed 80%. (3) The position of the reflux hole significantly affectsthe average pressure on each monitoring surface. (4) Placing the reflux hole at a excessively distant radial distancecan result in an excessive vertical component. (5) The self-priming performance of the pump can be improved tosome extent by placing the return hole at a small radial distance.
基金supported by the program for National Natural Science Foundation of China (Nos. 52174173, 52274188, and 52104190)the Joint Funds of the National Natural Science Foundation of China (No. U24A2091)+1 种基金The Natural Science Foundation of Henan Polytechnic University (No. B2021-2)Double FirstClass Initiative of Safety and Energy Engineering (Henan Polytechnic University) (Nos. AQ20240703 and AQ20230304)。
文摘Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.
基金the National Key Research and Development Project of China(No.2019YFB 2005300)the Natural Science Foundation of Jiangsu Province(No.BK20220609)the National Natural Science Foundation of China(Grant Nos.52109106,52409122,and 12272187).
文摘During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforation as a cavitation-mitigation strategy,in this study several mixed-flow pump models incorporating perforations were developed.Numerical simulations were performed for configurations with circular holes positioned at different locations along the blade leading edge,and the computational results were validated against experimental measurements.The findings indicate that the location of the perforations plays a decisive role in cavitation suppression.Moving from the blade rim toward the hub along the leading edge,the critical net positive suction head,NPSH_(cr),initially decreases and subsequently increases,while remaining consistently lower than that of the reference non-perforated configuration.The perforations promote the transfer of high-pressure fluid from the pressure side to the suction side of the blade,thereby alleviating local low-pressure regions.This pressure compensation significantly reduces the extent of low-pressure zones in the vicinity of the perforations,leading to a marked suppression of cavitation both locally and downstream of the perforated regions.
基金supported by European Commission and is a part of the HORIZON2020 project RES Heatfunding from the European Union’s Horizon 2020 program in the field of research and innovation on the basis of grant agreement No.956255.
文摘Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and renewable energy sources while considering operational constraints of existing systems.This study investigates a hybrid heating system combining a natural gas boiler(NGB)with an air-to-water heat pump(AWHP),evaluated through a combination of laboratory experiments and dynamic modelling.A prototype developed in the Electrical and Energy Engineering Laboratory enabled the characterization of both heat generators,the collection of experimental data,and the calibration of a MATLAB/Simulink model,including emissions and exhaust analyses.Sensitivity analyses were performed to identify optimal configurations for energy efficiency and system control,accounting for interactions between subsystems.Results highlight that hybridisation significantly improves primary energy efficiency and reduces fuel consumption compared to conventional NGB-only systems.Environmental performance,assessed through CO_(2) and NOx emissions and renewable energy integration,demonstrates the benefits of partial electrification in the residential sector.Economic assessment further quantifies decarbonization costs and fuel savings,illustrating tradeoffs between low-capital,moderate-performance systems and high-efficiency,high-renewable solutions requiring larger investments.The analysis shows that strategic decisions for residential decarbonisation cannot be separated from system-wide considerations,including control strategies,component integration,and economic feasibility.The study underlines the importance of hybrid and renewable-based solutions as pivotal pathways for energy transition in the residential building sector.
基金supported by the Henan Provincial Key Research and Development Special Project(251111220200)Natural Science Foundation of Henan Province Project(252300420446).
文摘To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.
文摘The self-priming process of a pump involves a complex gas-liquid two-phase flow.Studying the distribution of gas and water and the evolution of their flow in the pump is of great importance to optimize this process and shorten the pump self-priming time.In the present study,a standard k-εturbulence model and a multiphase flow model have been used to simulate the self-priming pump process considering four different reflux hole areas.A comparison of the distribution of air and water distribution on the axial surface and inside the volume have been carried out for the different considered cases.The pattern formed by the streamlines at different times during the whole self-priming process has also been investigated.The results show that the velocity at the trailing edge of the impeller outlet is the largest.The flow in the pump cavity is.complicated by the formation of vortices.The number,shape and location of the vortices change depending on the considered configuration.
基金supported by the National Natural Science Foundation of China(Project No.52377082)the Scientific Research Program of Jilin Provincial Department of Education(Project No.JJKH20230123KJ).
文摘Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.
基金The Fundamental Research Funds for the Central Universities(JD2423)。
文摘Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.
文摘In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.
基金supported by 2024 Central Guidance Local Science and Technology Development Fund Project"Study on the mechanism and evaluation method of thermal pollution in water bodies,as well as research on thermal carrying capacity".(Grant 246Z4506G)Key Research and Development Project in Hebei Province:"Key Technologies and Equipment Research and Demonstration of Multiple Energy Complementary(Electricity,Heat,Cold System)for Solar Energy,Geothermal Energy,Phase Change Energy"(Grant 236Z4310G)the Hebei Academy of Sciences Key Research and Development Program"Research on Heat Transfer Mechanisms and Efficient Applications of Intermediate and Deep Geothermal Energy"(22702)。
文摘Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.
基金supported in part by the National Nat-ural Science Foundation of China(52177110)Key Pro-gram of the National Natural Science Foundation of China(U22B20106,U2142206)+2 种基金Shenzhen Science and Technology Program(JCYJ20210324131409026)the Science and Technology Project of the State Grid Corpo-ration of China(5200-202319382A-2-3-XG)State Grid Zhejiang Elctric Power Co.,Ltd.Science and Tech-nology Project(B311DS24001A).
文摘Typhoons can cause large-area blackouts or partial outages of distribution networks.We define a partial outage state in the distribution network as a gray state and propose a gray-start strategy and two-stage distribution network emergency recovery framework.A phase-space reconstruction and stacked integrated model for predicting wind and photovoltaic generation during typhoon disasters is proposed in the first stage.This provides guidance for second-stage post-disaster emergency recovery scheduling.The emergency recovery scheduling model is established in the second stage,and this model is supported by a thermal power-generating unit,mobile emergency generators,and distributed generators.Distributed generation includes wind power generation,photovoltaics,fuel cells,etc.Simultaneously,we con-sider the gray-start based on the pumped storage unit to be an important first step in the emergency recovery strategy.This model is val-idated on the improved IEEE 33 node system,which utilizes data from the 2022 super typhoon“Muifa”in Zhoushan,Zhejiang,China.Simulations indicate the superiority of a gray start with a pumped storage unit and the proposed emergency recovery strategy.
文摘BACKGROUND Proton pump inhibitors(PPIs)are widely used,including among cancer patients,to manage gastroesophageal reflux and other gastric acid-related disorders.Recent evidence suggests associations between long-term PPI use and higher risks for various adverse health outcomes,including greater mortality.AIM To investigate the association between PPI use and all-cause mortality among cancer patients by a comprehensive analysis after adjustment for various confounders and a robust methodological approach to minimize bias.METHODS This retrospective cohort study used data from the TriNetX research network,with electronic health records from multiple healthcare organizations.The study employed a new-user,active comparator design,which compared newly treated PPI users with non-users and newly treated histamine2 receptor antagonists(H2RA)users among adult cancer patients.Newly prescribed PPIs(esomeprazole,lansoprazole,omeprazole,pantoprazole,or rabeprazole)users were compared to non-users or newly prescribed H2RAs(cimetidine,famotidine,nizatidine,or ranitidine)users.The primary outcome was all-cause mortality.Each patient in the main group was matched to a patient in the control group using 1:1 propensity score matching to reduce confounding effects.Multivariable Cox regression models were used to estimate hazard ratios(HRs)and 95% confidence interval(CI).RESULTS During the follow-up period(median 5.4±1.8 years for PPI users and 6.5±1.0 years for non-users),PPI users demonstrated a higher all-cause mortality rate than non-users after 1 year,2 years,and at the end of follow up(HRs:2.34-2.72).Compared with H2RA users,PPI users demonstrated a higher rate of all-cause mortality HR:1.51(95%CI:1.41-1.69).Similar results were observed across sensitivity analyses by excluding deaths from the first 9 months and 1-year post-exposure,confirming the robustness of these findings.In a sensitivity analysis,we analyzed all-cause mortality outcomes between former PPI users and individuals who have never used PPIs,providing insights into the long-term effects of past PPI use.In addition,at 1-year follow-up,the analysis revealed a significant difference in mortality rates between former PPI users and non-users(HR:1.84;95%CI:1.82-1.96).CONCLUSION PPI use among cancer patients was associated with a higher risk of all-cause mortality compared to non-users or H2RA users.These findings emphasize the need for cautious use of PPIs in cancer patients and suggest that alternative treatments should be considered when clinically feasible.However,further studies are needed to corroborate our findings,given the significant adverse outcomes in cancer patients.
基金supported by the Presidential Foundation of CAEP(Grant No.YZJJZL2023116)the National Nature Science Foundation of China(Grant No.12275249)the Youth Talent Fund of the Laser Fusion Research Center,CAEP(Grant Nos.RCFCZ7-2024-2 and RCFPD4-2020-4).
文摘We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.
文摘The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this study is to carry out a comparative analysis of two dewatering pumping systems (Solar Kit and GMP) for water mobilization on a certain number of criteria such as sustainable use, economic aspect and performance. To achieve this, the adapted methodology consisted first of all in the development of a data collection tool in the field. Then flow measurements, estimation of fuel consumption, pressure height, etc., were carried out. Thus, the data collection involved a sample of 120 irrigators who had to use the two (2) types of pumping systems. The collected data were analyzed and processed with appropriate software. The results of the study show that the two pumping systems studied have strengths and constraints. Thus, the solar pumping system has a significant investment cost, very low maintenance and a low operating cost. On the other hand, the system with a generator has a relatively low investment cost (25 to 30 times less than solar), but a relatively high operating, upkeep and maintenance cost. He adds that these assets and constraints must be taken into consideration when an investment is made. This study shows that 74% of producers use GMP compared to 26% who use the Solar Kit. But in practice, the Solar Kit is more reliable for producers from the point of view of planted area, environmental management and investment costs, supply of fuel and lubricant. These results indicate better performance of the solar pumping system compared to GMP at the study sites.
基金funded by China Oilfield Services Limited,grant number YXB24YF003.
文摘Jet pumps often suffer from efficiency losses due to the intense mixing of power and suction fluids,which leads to significant kinetic energy dissipation.Enhancing the efficiency of such pumps requires careful optimization of their structural parameters.In this study,a computational fluid dynamics(CFD)model of a hydraulic jet sand-flushing pump is developed to investigate the effects of throat-to-nozzle distance,area ratio,and throat length on the pump’s sand-carrying performance.An orthogonal experimental design is employed to optimize the structural parameters,while the influence of sand characteristics on pumping performance is systematically evaluated.Complementary indoor experiments are used to validate the numerical results,yielding an optimized configuration with a throat-to-nozzle cross-sectional area ratio of 4,a throat length five times the throat diameter,and a throat-to-nozzle distance equal to the nozzle diameter.Under a power fluid flow rate of 1.7 m3/h with this area ratio,the sand-carrying efficiency reaches its peak,achieving a sand transport rate of 290 g/min(6.7 L/h).Comparison of CFD predictions with experimental data across different area ratios demonstrates excellent agreement,with an average relative error of 2.44%and an average absolute error of 3.56%,confirming the reliability of the simulation approach.
基金supported by the National Natural Science Foundation of China(Research Project No.52169018).
文摘Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps.Prolonged cavitation can cause significant damage to the components of the flow channel,and in severe cases,it may even interfere with the normal energy exchange processes within the pump.Therefore,effective monitoring of cavitation in centrifugal pumps is crucial.This article presents a study that approaches the issue from an acoustic perspective,using experimental methods to gather and analyze acoustic data at the inlet and outlet of centrifugal pumps across various flow rates,with hydrophones as the primary measuring instruments.Results show that flow rate significantly affects noise levels in both non-cavitation and mild cavitation stages,with noise increasing as the flow rate rises.As the cavitation margin(NPSHa)decreases,inlet and outlet noise trends diverge:inlet noise drops sharply,while outlet noise initially increases before sharply decreasing.Both exhibit a distinct zone of abrupt change,where NPSHa values offer earlier cavitation detection than traditional methods.The noise at the pump’s inlet and outlet primarily consists of discrete and broadband noise,with most energy concentrated at discrete frequencies—shaft frequency(24 Hz),blade frequency(144 Hz),and their harmonics.As NPSHa decreases,the inlet’s discrete and broadband noise frequencies decline,while they increase at the outlet.Monitoring changes in these spectrum characteristics provides an additional means of predicting cavitation onset.
基金Supported by National Natural Science Foundation of China(Grant No.52205072).
文摘Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high efficiency and reliability.However,the ambiguity surrounding the output flow characteristics of individual two-dimensional pumps poses a significant challenge in achieving precise closed-loop control of the EHA positions.To address this issue,this study established a comprehensive numerical model that included gap leakage to analyze the impact of leakage on the output flow characteristics of a two-dimensional piston pump.The validity of the numerical analysis was indirectly confirmed through meticulous measurements of the leakage and volumetric efficiency,ensuring robust results.The research findings indicated that,at lower pump speeds,leakage significantly affected the output flow rate,leading to potential inefficiencies in the system.Conversely,at higher rotational speeds,the impact of leakage was less pronounced,implying that the influence of leakage on the pump outlet flow must be carefully considered and managed for EHAs to perform position servo control.Additionally,the research demonstrates that two-dimensional motion does not have a unique or additional effect on pump leakage,thus simplifying the design considerations.Finally,the study concluded that maintaining an oil-filled leakage environment is beneficial because it helps reduce the impact of leakage and enhances the overall volumetric efficiency of the pump system.
