This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined d...This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.展开更多
This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed...This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed‐loop coils are promising for many easily‐quenching direct‐current(DC)applications,where their performance is determined by magnetomotive forces,total number of turns,and dimensions.As the primary interface parameter in an application system,the operational current must be accurately and rapidly measured.Generally,this is achieved by dividing the measured magnetic field by the coil constant.However,even if the influence of the screening current induced field(SCIF)is not considered,existing methods for the coil constant may be disturbed by the performance and location of Hall sensors,or experience a long measuring period.Therefore,a relatively accurate and fast method is proposed in this study,which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator.The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method(FEM)model,and its current accuracy can be equivalent to the resolution of the employed power supply.It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location,and has a more reliable accuracy in contrast to the simulation method.Compared to the experimentally conventional method,the proposed method presents a significantly faster speed.The impact of the SCIF was considered and proven to be negligible for the tested pancake coils.Even for coils whose coil constant vibrates owing to the SCIF,this method can be adapted to directly measure various operational currents.Furthermore,it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM,and a procedure for reducing this error was proposed.展开更多
Goal oriented( GO) methodology is a kind of success oriented system reliability analysis method and has been used widely.The repairable system with dual input closed-loop feedback link( DICLFL) considering shutdown co...Goal oriented( GO) methodology is a kind of success oriented system reliability analysis method and has been used widely.The repairable system with dual input closed-loop feedback link( DICLFL) considering shutdown correlation didn't make reliability analysis accurately based on existing GO methodology. So, a reliability analysis method used to deal with DICLFL considering shutdown correlation is provided based on GO methodology.Firstly, a new operator, which is used to describe DICLFL considering shutdown correlation,whose number is 1,is created and named as Type 9C operator. And then,the formulas of type 9C operator are derived based on Markov process theory. Finally,the new method presented in this paper is adopted to conduct the reliability analysis of an electro-hydraulic servo speed control system. The analysis result is compared with those of Monte Carlo simulation and fault tree analysis( FTA). The comparison results show that this new reliability analysis method based on GO methodology is feasible and meaningful for reliability analysis of repairable systems with DICLFL considering shutdown correlation.Meantime,it will be useful for more other applications.展开更多
合环电流评估技术对于配电网馈线合环转供电操作具有重要意义,为了提高主动配电网馈线合环电流计算的准确性,文中从融入源荷数据分布特性及预测的角度,提出基于双重K2算法和概率潮流(double K2 algorithm and probability load flow,DK2...合环电流评估技术对于配电网馈线合环转供电操作具有重要意义,为了提高主动配电网馈线合环电流计算的准确性,文中从融入源荷数据分布特性及预测的角度,提出基于双重K2算法和概率潮流(double K2 algorithm and probability load flow,DK2-PLF)的主动配电网馈线合环电流评估方法。首先,采用基于DK2算法的贝叶斯网络描述源荷相关性样本;其次,利用Cholesky分解方法处理获得的源荷相关性样本,以半不变量法计算主动配电网馈线合环电流的累积概率分布;然后,对主动配电网馈线合环电流从合环成功率和越限程度两方面进行安全性评估;最后,以贵州某城市为算例,对10 kV配电网系统开展馈线合环电流评估研究。得出以下结论:一是从概率密度、累积分布、最大误差三方面比较,相比于K2算法,DK2算法源荷预测值的概率密度、累积分布误差较小,验证了DK2算法的优越性;二是从累积分布、最大误差两方面比较,采用Cholesky分解的半不变量法对比未采用Cholesky分解的半不变量法、蒙特卡洛法,其累积分布误差较小,采用Cholesky分解的半不变量法满足主动配电网馈线合环电流评估要求;三是从合环成功率、合环越限程度两方面比较,采用半不变量法计算的合环电流安全性指标结果与仿真结果偏差在电网经验误差5%范围内,说明基于DK2-PLF的主动配电网馈线合环电流评估方法可为合环辅助决策提供参考。展开更多
This paper proposes a kind of optimization software for substation operation mode, which can not only read data on-line from EMS, but also calculate total loss of substations in parallel operation, split operation or ...This paper proposes a kind of optimization software for substation operation mode, which can not only read data on-line from EMS, but also calculate total loss of substations in parallel operation, split operation or individual operation mode. It can also select the most optimized way and feed the conclusion back to EMS to make substations operate in the most optimized way. The software is suitable for optimization of substation in rural power grid.展开更多
基金the Ger man National Science Foundation (GR-412/33-2)Shanghai Leading Academic Discipline Project (No.B604)
文摘This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.
基金supported by National Natural Science Foundation of China(NSFC)under project 51977130.
文摘This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed‐loop coils are promising for many easily‐quenching direct‐current(DC)applications,where their performance is determined by magnetomotive forces,total number of turns,and dimensions.As the primary interface parameter in an application system,the operational current must be accurately and rapidly measured.Generally,this is achieved by dividing the measured magnetic field by the coil constant.However,even if the influence of the screening current induced field(SCIF)is not considered,existing methods for the coil constant may be disturbed by the performance and location of Hall sensors,or experience a long measuring period.Therefore,a relatively accurate and fast method is proposed in this study,which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator.The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method(FEM)model,and its current accuracy can be equivalent to the resolution of the employed power supply.It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location,and has a more reliable accuracy in contrast to the simulation method.Compared to the experimentally conventional method,the proposed method presents a significantly faster speed.The impact of the SCIF was considered and proven to be negligible for the tested pancake coils.Even for coils whose coil constant vibrates owing to the SCIF,this method can be adapted to directly measure various operational currents.Furthermore,it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM,and a procedure for reducing this error was proposed.
基金Technical Basis Projects of China's MIIT(Nos.ZQ092012B003,2012090003)
文摘Goal oriented( GO) methodology is a kind of success oriented system reliability analysis method and has been used widely.The repairable system with dual input closed-loop feedback link( DICLFL) considering shutdown correlation didn't make reliability analysis accurately based on existing GO methodology. So, a reliability analysis method used to deal with DICLFL considering shutdown correlation is provided based on GO methodology.Firstly, a new operator, which is used to describe DICLFL considering shutdown correlation,whose number is 1,is created and named as Type 9C operator. And then,the formulas of type 9C operator are derived based on Markov process theory. Finally,the new method presented in this paper is adopted to conduct the reliability analysis of an electro-hydraulic servo speed control system. The analysis result is compared with those of Monte Carlo simulation and fault tree analysis( FTA). The comparison results show that this new reliability analysis method based on GO methodology is feasible and meaningful for reliability analysis of repairable systems with DICLFL considering shutdown correlation.Meantime,it will be useful for more other applications.
文摘合环电流评估技术对于配电网馈线合环转供电操作具有重要意义,为了提高主动配电网馈线合环电流计算的准确性,文中从融入源荷数据分布特性及预测的角度,提出基于双重K2算法和概率潮流(double K2 algorithm and probability load flow,DK2-PLF)的主动配电网馈线合环电流评估方法。首先,采用基于DK2算法的贝叶斯网络描述源荷相关性样本;其次,利用Cholesky分解方法处理获得的源荷相关性样本,以半不变量法计算主动配电网馈线合环电流的累积概率分布;然后,对主动配电网馈线合环电流从合环成功率和越限程度两方面进行安全性评估;最后,以贵州某城市为算例,对10 kV配电网系统开展馈线合环电流评估研究。得出以下结论:一是从概率密度、累积分布、最大误差三方面比较,相比于K2算法,DK2算法源荷预测值的概率密度、累积分布误差较小,验证了DK2算法的优越性;二是从累积分布、最大误差两方面比较,采用Cholesky分解的半不变量法对比未采用Cholesky分解的半不变量法、蒙特卡洛法,其累积分布误差较小,采用Cholesky分解的半不变量法满足主动配电网馈线合环电流评估要求;三是从合环成功率、合环越限程度两方面比较,采用半不变量法计算的合环电流安全性指标结果与仿真结果偏差在电网经验误差5%范围内,说明基于DK2-PLF的主动配电网馈线合环电流评估方法可为合环辅助决策提供参考。
文摘This paper proposes a kind of optimization software for substation operation mode, which can not only read data on-line from EMS, but also calculate total loss of substations in parallel operation, split operation or individual operation mode. It can also select the most optimized way and feed the conclusion back to EMS to make substations operate in the most optimized way. The software is suitable for optimization of substation in rural power grid.
