As a key component of injection molding,multi-cavity hot runner(MCHR)system faces the crucial problem of polymer melt filling imbalance among the cavities.The thermal imbalance in the system has been considered as the...As a key component of injection molding,multi-cavity hot runner(MCHR)system faces the crucial problem of polymer melt filling imbalance among the cavities.The thermal imbalance in the system has been considered as the leading cause.Hence,the solution may rest with the synchronization of those heating processes in MCHR system.This paper proposes a’Master-Slave’generalized predictive synchronization control(MS-GPSC)method with’Mr.Slowest’strategy for preheating stage of MCHR system.The core of the proposed method is choosing the heating process with slowest dynamics as the’Master’to track the setpoint,while the other heating processes are treated as‘Slaves’tracking the output of’Master’.This proposed method is shown to have the good ability of temperature synchronization.The corresponding analysis is conducted on parameters tuning and stability,simulations and experiments show the strategy is effective.展开更多
In this study, we propose a new temperature compensation control strategy for a multi-cavity hot runner injection molding system, At first, the melt filling time of each cavity can be measured by installing temperatur...In this study, we propose a new temperature compensation control strategy for a multi-cavity hot runner injection molding system, At first, the melt filling time of each cavity can be measured by installing temperature sensors on the position around end filling area, and filling time difference between the various cavities can be calculated. Then the melt temperature of each hot nozzle can be adjusted automatically by a control strategy established based on the Fuzzy Theory and a program compiled with LABVIEW software. Temperature changes the melt mobility, so the adjustment of temperature can equalize the filling time of the melt in each cavity, which can reduced the mass deviation between each cavity and make product properties of each cavity consistent. The conclusion of the experiment is as follows： For this contact lens box of a four-cavity Hot Runner mold, by applying hot runner temperature compensation control system, time difference can be reduced from 0.05 s to 0.01 s at each cavity, and the mass Standard deviation of the four cavity can be improved from 0.006 to 0.002. The ratio of imbalance can be reduced from 20% to 4%. Hence, the hot runner temperature compensation control system has significant feasibility and high potential in improving melt flow balance of multi-cavity molding application.展开更多
In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h...In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.展开更多
Background:Despite the wide use of compression garments to enhance athletic running performance,evidence supporting improvements has not been conclusive.This updated systematic review and meta-analysis of randomized c...Background:Despite the wide use of compression garments to enhance athletic running performance,evidence supporting improvements has not been conclusive.This updated systematic review and meta-analysis of randomized controlled trials(RCTs)compared the effects of compression garment wearing with those of non-compression garment wearing(controls)during running on improving running performance.Methods:A comprehensive search was conducted in the electronic databases(Web of Science,EBSCOhost,PubMed,Embase,Scopus,and Cochrane)for RCTs comparing running performance between runners wearing compression garments and controls during running,from inception to September 2024.Independent reviewers screened studies,extracted data,appraised risk of bias(RoB 2)and certainty of evidence(Grading of Recommendations Assessments,Development and Evaluation(GRADE)).Primary outcomes were race time and time to exhaustion.Secondary outcomes covered running speed and race pace,submaximal oxygen uptake,tissue oxygenation,and soft tissue vibration.Randomeffects meta-analyses were conducted to generate pooled estimates,expressed in standardized mean difference(SMD).Subgroup differences of garment,race type,and contact surface were tested in moderator analyses.Results:The search yielded 51 eligible studies comprising 899 participants,of which 33 studies were available for meta-analysis of primary outcomes.Runners wearing compression garments during running showed no significant improvement in race time(SMD=-0.07,95%CI:-0.22 to 0.09;p=0.40)or time to exhaustion(SMD=0.04,95%CI:-0.20 to 0.29;p=0.72).Moderator analyses indicated no effects from garment type,race type,or surface.Secondary outcomes also showed no performance benefits,although compression garments significantly reduced soft tissue vibration(SMD=-0.43,95%CI:-0.70 to-0.15;p<0.01).Certainty of evidence was rated low to very low.Conclusion:Data synthesis of current RCTs offers no updated evidence favoring the support of wearing compression garments during running as a viable strategy for improving running and endurance performance among runners of varying performance levels and types of running races.展开更多
Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Elect...Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Electronic databases were searched for literature dating from January 2000 to October 2015. The search was conducted using the key words "high-intensity intermittent training" or "high-intensity interval exercise" or "interval running" or "sprint interval training" and "endurance runners" or "long distance runners". A systematic approach was used to evaluate the 783 articles identified for initial review. Studies were included if they investigated HIIT in recreational endurance runners. The methodological quality of the studies was evaluated using the Physiotherapy Evidence Database(PEDro) scale(for intervention studies) and the modified Downs and Black Quality Index(for cross-sectional studies).Results: Twenty-three studies met the inclusionary criteria for review. The results are presented in 2 parts: cross-sectional(n = 15) and intervention studies(n = 8). In the 15 cross-sectional studies selected, endurance runners performed at least 1 HIIT protocol, and the acute impact on physiological, neuromuscular, metabolic and/or biomechanical variables was assessed. Intervention studies lasted a minimum of 4 weeks, with 10 weeks being the longest intervention period, and included 2 to 4 HIIT sessions per week. Most of these studies combined HIIT sessions with continuous run(CR) sessions; 2 studies' subjects performed HIIT exclusively.Conclusion: HIIT-based running plans(2 to 3 HIIT sessions per week, combining HIIT and CR runs) show athletic performance improvements in endurance runners by improving maximal oxygen uptake and running economy along with muscular and metabolic adaptations. To maximize the adaptations to training, both HIIT and CR must be part of training programs for endurance runners.展开更多
Purpose:This umbrella systematic review(SR) of SRs and meta-analysis seeks to comprehensively synthesize existing literature to identify and consolidate the diverse range of risk factors contributing to running-relate...Purpose:This umbrella systematic review(SR) of SRs and meta-analysis seeks to comprehensively synthesize existing literature to identify and consolidate the diverse range of risk factors contributing to running-related injuries(RRIs).Methods:Systematic searches were conducted on June 28,2023,across Web of Science,SPORTDiscus,Scopus,PubMed,and Cochrane Library.We included SRs,whether accompanied by meta-analyses or not,that focused on investigating risk factors for RRIs within observational studies.The methodological quality of the SRs was evaluated using the Assessing the Methodological Quality of Systematic Reviews Ⅱ.To assess the extent of overlap across reviews,the corrected covered area metric was calculated.Results:From 1509 records retrieved,13 SRs were included.The degree of overlap between SRs was low(4%),and quality varied from critically low(n=8) to low(n=5).Two hundred seven outcomes assessed in 148 primary studies were identified as being associated with the occurrence of RRIs.The effect sizes of the associations for which risk measures were reported(n=131) were classified as large(n=30,23%),medium(n=38,29%),small(n=48,37%) or no effect(n=15,11%).Running/training characteristics,health and lifestyle factors,along with morphological and biomechanical aspects,exhibit large effect sizes in increasing the risk for RRIs.Conclusion:Drawing from the outcomes of the low-quality SRs and associations with large effect sizes,our findings indicate that running/training characteristics and health and lifestyle factors,as well as morphological and biomechanical aspects,are all implicated in elevating the risk of RRIs,emphasizing the multifactorial basis of injury incidence in running.Given the low quality and heterogeneity of SR,individual findings warrant cautious interpretation.展开更多
In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t...In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t runner systems are being applied in the moulding industry to save material and decrease the losses of injection pressure. Heat transfer from hot runner system from the fixed half which is secured in the fix machine platen could transmit s o much heat that it may cause high temperature differential between the machine fix platen and moving platen. This will cause the tie bar to become unparallel. Part quality will be compromised and the wear of the tie bar will be excessive. Overhaul of the tie bar may be necessary after a short period of time which is c ostly. This raises the need to analyze the heat transfer from the hot runner sys tem to the machine fix platen and the methods of isolating or minimizing the hea t transfer. In this case study, a photo lens article mould was used. The mould w as built with a direct hot runner nozzle system. Heat conduction from hot runner and machine screw to machine fix platen were studied based on either using high temperature heat insulating plate put in placed between the mould and the mould ing machine fix platen or drill cooling channels in the front mould clamping pla te. The high temperature insulator is very costly as it is made out of glass re inforced polymer composite material. Experimental results were obtained and anal yzed to find the best method to minimize the unwanted heat transfer using the ch eapest and most effective method.展开更多
This novel is mainly about how Khaled Hosseini presents the nature of human and the social development by depicting the symbol"Kite".And the"Kite"also created a poetic atmosphere and emotion for th...This novel is mainly about how Khaled Hosseini presents the nature of human and the social development by depicting the symbol"Kite".And the"Kite"also created a poetic atmosphere and emotion for the works,strengthening the shaping of image,enriching the spatial narrative dimension,enhancing the novel subject and made Khaled Hosseini,a Diasporas writer recognized by the main stream of American society.展开更多
This article analyzes The Kite Runner with the help of spactial narrative. The novel will be analyzed from three angles—the function of spatial narrative, the basic unit of spatial narrative, the periphery of spatial...This article analyzes The Kite Runner with the help of spactial narrative. The novel will be analyzed from three angles—the function of spatial narrative, the basic unit of spatial narrative, the periphery of spatial narrative and the overall effect presented in the novel by using these narrative techniques.展开更多
The pressure fluctuation caused by unsteady flow in runner is one of the main reasons of vibration for a large Francis hydraulic turbine. It directly affects the steady operation of the hydraulic turbine unit. The exi...The pressure fluctuation caused by unsteady flow in runner is one of the main reasons of vibration for a large Francis hydraulic turbine. It directly affects the steady operation of the hydraulic turbine unit. The existing research of the pressure fluctuation in hydraulic turbine mainly focuses on the unsteady flow in draft tube. Accurate distribution of pressure fluctuations inside a runner is not very clear. In this paper, the numerical method for predicting the pressure fluctuations in runner is investigated and the numerical simulation is performed for a large Francis hydraulic turbine. It is proved that the combination of shear-stress transport（SST） k-o） turbulence model and pressure-implicit with splitting of operators（PISO） algorithm could give more reliable prediction of pressure fluctuations in runner. The frequencies of pressure fluctuations in runner are affected by the flow in guide vane and the flow in draft tube The first dominant frequency is significantly determined by the flow in draft tube, especially at part load condition. This frequency is approximately equal to one-third of the runner rotating frequency. The evident second dominant frequency is exactly equal to the guide vane passing frequency. The peak-to-peak amplitudes of pressure fluctuations in runner at small guide vane open angle are larger than that at large open angle at the same operating head. The amplitudes at points on blade pressure surface are generally greater than that on suction surface. The research results could be used to direct the hydraulic design and operation stability improvement of a large Francis hydraulic turbine.展开更多
To improve the design speed and reduce the design cost for the previous blade design method, a modified inverse design method is presented. In the new method, after a series of physical and mathematical simplification...To improve the design speed and reduce the design cost for the previous blade design method, a modified inverse design method is presented. In the new method, after a series of physical and mathematical simplifications, a sail?like constrained area is proposed, which can be used to configure di erent runner blade shapes. Then, the new method is applied to redesign and optimize the runner blade of the scale core component of the 1400?MW canned nuclear coolant pump in an established multi?optimization system compromising the Computational Fluid Dynamics(CFD) analysis, the Response Surface Methodology(RSM) and the Non?dominated Sorting Genetic Algorithm?II(NSGA?II). After the execution of the optimization procedure, three optimal samples were ultimately obtained. Then, through comparative analysis using the target runner blade, it was found that the maximum e ciency improvement reached 1.6%, while the head improvement was about 10%. Overall, a promising runner blade inverse design method which will benefit the hydraulic design of the mixed?flow pump has been proposed.展开更多
基金supported in part by National Natural Science Foundation of China(62203127)Basic and Applied Basic Research Project of Guangzhou City(2023A04J1712)+1 种基金The Foshan-HKUST Projects Program(FSUST19-FYTRI01)GDAS’Project of Science and Technology Development(2020GDASYL-20200202001).
文摘As a key component of injection molding,multi-cavity hot runner(MCHR)system faces the crucial problem of polymer melt filling imbalance among the cavities.The thermal imbalance in the system has been considered as the leading cause.Hence,the solution may rest with the synchronization of those heating processes in MCHR system.This paper proposes a’Master-Slave’generalized predictive synchronization control(MS-GPSC)method with’Mr.Slowest’strategy for preheating stage of MCHR system.The core of the proposed method is choosing the heating process with slowest dynamics as the’Master’to track the setpoint,while the other heating processes are treated as‘Slaves’tracking the output of’Master’.This proposed method is shown to have the good ability of temperature synchronization.The corresponding analysis is conducted on parameters tuning and stability,simulations and experiments show the strategy is effective.
文摘In this study, we propose a new temperature compensation control strategy for a multi-cavity hot runner injection molding system, At first, the melt filling time of each cavity can be measured by installing temperature sensors on the position around end filling area, and filling time difference between the various cavities can be calculated. Then the melt temperature of each hot nozzle can be adjusted automatically by a control strategy established based on the Fuzzy Theory and a program compiled with LABVIEW software. Temperature changes the melt mobility, so the adjustment of temperature can equalize the filling time of the melt in each cavity, which can reduced the mass deviation between each cavity and make product properties of each cavity consistent. The conclusion of the experiment is as follows： For this contact lens box of a four-cavity Hot Runner mold, by applying hot runner temperature compensation control system, time difference can be reduced from 0.05 s to 0.01 s at each cavity, and the mass Standard deviation of the four cavity can be improved from 0.006 to 0.002. The ratio of imbalance can be reduced from 20% to 4%. Hence, the hot runner temperature compensation control system has significant feasibility and high potential in improving melt flow balance of multi-cavity molding application.
文摘In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.
基金supported by the National Natural Science Foundation of China(Grant No.NSFC11932013)National Key Research and Development Program of China(Grant No.2022YFB3805800).
文摘Background:Despite the wide use of compression garments to enhance athletic running performance,evidence supporting improvements has not been conclusive.This updated systematic review and meta-analysis of randomized controlled trials(RCTs)compared the effects of compression garment wearing with those of non-compression garment wearing(controls)during running on improving running performance.Methods:A comprehensive search was conducted in the electronic databases(Web of Science,EBSCOhost,PubMed,Embase,Scopus,and Cochrane)for RCTs comparing running performance between runners wearing compression garments and controls during running,from inception to September 2024.Independent reviewers screened studies,extracted data,appraised risk of bias(RoB 2)and certainty of evidence(Grading of Recommendations Assessments,Development and Evaluation(GRADE)).Primary outcomes were race time and time to exhaustion.Secondary outcomes covered running speed and race pace,submaximal oxygen uptake,tissue oxygenation,and soft tissue vibration.Randomeffects meta-analyses were conducted to generate pooled estimates,expressed in standardized mean difference(SMD).Subgroup differences of garment,race type,and contact surface were tested in moderator analyses.Results:The search yielded 51 eligible studies comprising 899 participants,of which 33 studies were available for meta-analysis of primary outcomes.Runners wearing compression garments during running showed no significant improvement in race time(SMD=-0.07,95%CI:-0.22 to 0.09;p=0.40)or time to exhaustion(SMD=0.04,95%CI:-0.20 to 0.29;p=0.72).Moderator analyses indicated no effects from garment type,race type,or surface.Secondary outcomes also showed no performance benefits,although compression garments significantly reduced soft tissue vibration(SMD=-0.43,95%CI:-0.70 to-0.15;p<0.01).Certainty of evidence was rated low to very low.Conclusion:Data synthesis of current RCTs offers no updated evidence favoring the support of wearing compression garments during running as a viable strategy for improving running and endurance performance among runners of varying performance levels and types of running races.
基金the University of Jaén for its support to the present study
文摘Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Electronic databases were searched for literature dating from January 2000 to October 2015. The search was conducted using the key words "high-intensity intermittent training" or "high-intensity interval exercise" or "interval running" or "sprint interval training" and "endurance runners" or "long distance runners". A systematic approach was used to evaluate the 783 articles identified for initial review. Studies were included if they investigated HIIT in recreational endurance runners. The methodological quality of the studies was evaluated using the Physiotherapy Evidence Database(PEDro) scale(for intervention studies) and the modified Downs and Black Quality Index(for cross-sectional studies).Results: Twenty-three studies met the inclusionary criteria for review. The results are presented in 2 parts: cross-sectional(n = 15) and intervention studies(n = 8). In the 15 cross-sectional studies selected, endurance runners performed at least 1 HIIT protocol, and the acute impact on physiological, neuromuscular, metabolic and/or biomechanical variables was assessed. Intervention studies lasted a minimum of 4 weeks, with 10 weeks being the longest intervention period, and included 2 to 4 HIIT sessions per week. Most of these studies combined HIIT sessions with continuous run(CR) sessions; 2 studies' subjects performed HIIT exclusively.Conclusion: HIIT-based running plans(2 to 3 HIIT sessions per week, combining HIIT and CR runs) show athletic performance improvements in endurance runners by improving maximal oxygen uptake and running economy along with muscular and metabolic adaptations. To maximize the adaptations to training, both HIIT and CR must be part of training programs for endurance runners.
基金supported by the Programa de Bolsas Universitarias de Santa CatarinaBrasil(Uniedu)(Grant No.14786,Grant No.16479)the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior(CAPES).
文摘Purpose:This umbrella systematic review(SR) of SRs and meta-analysis seeks to comprehensively synthesize existing literature to identify and consolidate the diverse range of risk factors contributing to running-related injuries(RRIs).Methods:Systematic searches were conducted on June 28,2023,across Web of Science,SPORTDiscus,Scopus,PubMed,and Cochrane Library.We included SRs,whether accompanied by meta-analyses or not,that focused on investigating risk factors for RRIs within observational studies.The methodological quality of the SRs was evaluated using the Assessing the Methodological Quality of Systematic Reviews Ⅱ.To assess the extent of overlap across reviews,the corrected covered area metric was calculated.Results:From 1509 records retrieved,13 SRs were included.The degree of overlap between SRs was low(4%),and quality varied from critically low(n=8) to low(n=5).Two hundred seven outcomes assessed in 148 primary studies were identified as being associated with the occurrence of RRIs.The effect sizes of the associations for which risk measures were reported(n=131) were classified as large(n=30,23%),medium(n=38,29%),small(n=48,37%) or no effect(n=15,11%).Running/training characteristics,health and lifestyle factors,along with morphological and biomechanical aspects,exhibit large effect sizes in increasing the risk for RRIs.Conclusion:Drawing from the outcomes of the low-quality SRs and associations with large effect sizes,our findings indicate that running/training characteristics and health and lifestyle factors,as well as morphological and biomechanical aspects,are all implicated in elevating the risk of RRIs,emphasizing the multifactorial basis of injury incidence in running.Given the low quality and heterogeneity of SR,individual findings warrant cautious interpretation.
文摘In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t runner systems are being applied in the moulding industry to save material and decrease the losses of injection pressure. Heat transfer from hot runner system from the fixed half which is secured in the fix machine platen could transmit s o much heat that it may cause high temperature differential between the machine fix platen and moving platen. This will cause the tie bar to become unparallel. Part quality will be compromised and the wear of the tie bar will be excessive. Overhaul of the tie bar may be necessary after a short period of time which is c ostly. This raises the need to analyze the heat transfer from the hot runner sys tem to the machine fix platen and the methods of isolating or minimizing the hea t transfer. In this case study, a photo lens article mould was used. The mould w as built with a direct hot runner nozzle system. Heat conduction from hot runner and machine screw to machine fix platen were studied based on either using high temperature heat insulating plate put in placed between the mould and the mould ing machine fix platen or drill cooling channels in the front mould clamping pla te. The high temperature insulator is very costly as it is made out of glass re inforced polymer composite material. Experimental results were obtained and anal yzed to find the best method to minimize the unwanted heat transfer using the ch eapest and most effective method.
文摘This novel is mainly about how Khaled Hosseini presents the nature of human and the social development by depicting the symbol"Kite".And the"Kite"also created a poetic atmosphere and emotion for the works,strengthening the shaping of image,enriching the spatial narrative dimension,enhancing the novel subject and made Khaled Hosseini,a Diasporas writer recognized by the main stream of American society.
文摘This article analyzes The Kite Runner with the help of spactial narrative. The novel will be analyzed from three angles—the function of spatial narrative, the basic unit of spatial narrative, the periphery of spatial narrative and the overall effect presented in the novel by using these narrative techniques.
基金supported by National Natural Science Foundation of China(Grant Nos. 51079152, 91010003, 51079151)Research Fund for the Doctoral Program of Higher Education of China(Grant No.0100008110012)Beijing Municipal Research Fund of Commission of Education of China(Grant No. 20100909)
文摘The pressure fluctuation caused by unsteady flow in runner is one of the main reasons of vibration for a large Francis hydraulic turbine. It directly affects the steady operation of the hydraulic turbine unit. The existing research of the pressure fluctuation in hydraulic turbine mainly focuses on the unsteady flow in draft tube. Accurate distribution of pressure fluctuations inside a runner is not very clear. In this paper, the numerical method for predicting the pressure fluctuations in runner is investigated and the numerical simulation is performed for a large Francis hydraulic turbine. It is proved that the combination of shear-stress transport（SST） k-o） turbulence model and pressure-implicit with splitting of operators（PISO） algorithm could give more reliable prediction of pressure fluctuations in runner. The frequencies of pressure fluctuations in runner are affected by the flow in guide vane and the flow in draft tube The first dominant frequency is significantly determined by the flow in draft tube, especially at part load condition. This frequency is approximately equal to one-third of the runner rotating frequency. The evident second dominant frequency is exactly equal to the guide vane passing frequency. The peak-to-peak amplitudes of pressure fluctuations in runner at small guide vane open angle are larger than that at large open angle at the same operating head. The amplitudes at points on blade pressure surface are generally greater than that on suction surface. The research results could be used to direct the hydraulic design and operation stability improvement of a large Francis hydraulic turbine.
基金National Basic Research Program of China(973 Program,Grant No.2015CB057301)Research and Innovation in Science and Technology Major Project of Liaoning Province,China(Grant No.201410001)Collaborative Innovation Center of Major Machine Manufacturing in Liaoning Province,China
文摘To improve the design speed and reduce the design cost for the previous blade design method, a modified inverse design method is presented. In the new method, after a series of physical and mathematical simplifications, a sail?like constrained area is proposed, which can be used to configure di erent runner blade shapes. Then, the new method is applied to redesign and optimize the runner blade of the scale core component of the 1400?MW canned nuclear coolant pump in an established multi?optimization system compromising the Computational Fluid Dynamics(CFD) analysis, the Response Surface Methodology(RSM) and the Non?dominated Sorting Genetic Algorithm?II(NSGA?II). After the execution of the optimization procedure, three optimal samples were ultimately obtained. Then, through comparative analysis using the target runner blade, it was found that the maximum e ciency improvement reached 1.6%, while the head improvement was about 10%. Overall, a promising runner blade inverse design method which will benefit the hydraulic design of the mixed?flow pump has been proposed.
