Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape not...Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.展开更多
Mathematical modelling for power DC/DC converters is a historical problem accompanying DC/DC conversion technology since 1940’s. The traditional mathematical modelling is not available for complex structure converter...Mathematical modelling for power DC/DC converters is a historical problem accompanying DC/DC conversion technology since 1940’s. The traditional mathematical modelling is not available for complex structure converters since the differential equation order increases very high. We have to search other way to establish mathematical modelling for power DC/DC converters.We have theoretically defined a new concept-Energy Factor （EF） in this paper and researched the relations between EF and the mathematical modelling for power DC/DC converters. EF is a new concept in power DC/DC conversion technology, which thoroughly differs from the traditional concepts such as power factor （PF）, power transfer efficiency （η）, total harmonic distortion （THD） and ripple factor （RF）. EF and the subsequential EFV (and EFVD) can illustrate the system stability, reference response and interference recovery. This investigation is very helpful for system design and DC/DC converters characteristics foreseeing. Two DC/DC converters: Buck converter and Super-Lift Luo-Converter as the samples are analysed in this paper to demonstrate the applications of EF, EFV (and EFVD), PE, SE, VE （and VED）, time constant τ and damping time constant τd.展开更多
Load of an automatic feed mechanism is composed of the stretching force of feed belt at the entrance to lower flexible guidance and the friction force between feed belt and flexible guidance. A mathematical model for ...Load of an automatic feed mechanism is composed of the stretching force of feed belt at the entrance to lower flexible guidance and the friction force between feed belt and flexible guidance. A mathematical model for computing the load was presented. An optimization problem was formulated to determine the attitude of the flexible guidance based on the principle that the potential energy stored in the system was the minimum at the equilibrium. Then the friction force was obtained according to the attitude of guide leaves and the moving velocity of the feed belt and the friction factor. Consequently, the load of the automatic feed mechanism can be calculated. Finally, an example was given to compute the load when the horizontal and elevating firing angles of the automation were respectively 45° and 30°. The computing result can be a criterion to determine the designing parameters of automat.展开更多
A novel cooling system combining ultra fast cooling rigs with laminar cooling devices was investigated.Based on the different cooling mechanisms,a serial of mathematic models were established to describe the relations...A novel cooling system combining ultra fast cooling rigs with laminar cooling devices was investigated.Based on the different cooling mechanisms,a serial of mathematic models were established to describe the relationship between water flow and spraying pressure and the relationship between water spraying heat flux and layout of nozzles installed on the top and bottom cooling headers.Model parameters were validated by measured data.Heat transfer models including air convection model,heat radiation model and water cooling capacity model were detailedly introduced.In addition,effects on cooling capacity by water temperature and different valve patterns were also presented.Finally,the comparison results from UFC used or not have been provided with respect to temperature evolution and mechanical properties of Q235B steel grade with thickness of 7.8 mm.Since online application of the sophisticated CTC process control system based on these models,run-out table cooling control system has been running stably and reliably to produce resource-saving,low-cost steels with smaller grain size.展开更多
文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比...文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比分析研究,数值模拟能够客观地反映起旋室旋流的流场特性,成果可为旋流溢洪道的研究应用提供参考.展开更多
为探讨莱州湾生态系统年代际变化,基于莱州湾1980年代(1980s)和2020年代(2020s)相关数据,应用Ecopath with Ecosim(EwE)软件,分别构建莱州湾1980s和2020s的Ecopath模型,对比莱州湾生态系统年代际的结构和功能差异。结果显示,两个年代莱...为探讨莱州湾生态系统年代际变化,基于莱州湾1980年代(1980s)和2020年代(2020s)相关数据,应用Ecopath with Ecosim(EwE)软件,分别构建莱州湾1980s和2020s的Ecopath模型,对比莱州湾生态系统年代际的结构和功能差异。结果显示,两个年代莱州湾生态系统均存在牧食食物链和碎屑食物链两种能量传递途径,能量流动主要集中在低营养级,能量流动规律符合金字塔逐级递减规律;与1980s相比,2020s莱州湾生态系统功能组营养级下降,生物量减少;2020s莱州湾流向碎屑量和系统总流量降低,资源再循环效率提高,总初级生产量/总呼吸量和系统净生产量降低,Finn’s循环指数和Finn’s平均路径长度增大,连接指数增大。研究表明,2020s莱州湾生态系统规模比1980s有所下降,生态系统的稳定性有所提高。展开更多
基金Project(51004085)supported by the National Natural Science Foundation of China
文摘Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.
文摘Mathematical modelling for power DC/DC converters is a historical problem accompanying DC/DC conversion technology since 1940’s. The traditional mathematical modelling is not available for complex structure converters since the differential equation order increases very high. We have to search other way to establish mathematical modelling for power DC/DC converters.We have theoretically defined a new concept-Energy Factor （EF） in this paper and researched the relations between EF and the mathematical modelling for power DC/DC converters. EF is a new concept in power DC/DC conversion technology, which thoroughly differs from the traditional concepts such as power factor （PF）, power transfer efficiency （η）, total harmonic distortion （THD） and ripple factor （RF）. EF and the subsequential EFV (and EFVD) can illustrate the system stability, reference response and interference recovery. This investigation is very helpful for system design and DC/DC converters characteristics foreseeing. Two DC/DC converters: Buck converter and Super-Lift Luo-Converter as the samples are analysed in this paper to demonstrate the applications of EF, EFV (and EFVD), PE, SE, VE （and VED）, time constant τ and damping time constant τd.
基金Project supported by the Seventh Research Institute of China State Shipbuilding Corporation
文摘Load of an automatic feed mechanism is composed of the stretching force of feed belt at the entrance to lower flexible guidance and the friction force between feed belt and flexible guidance. A mathematical model for computing the load was presented. An optimization problem was formulated to determine the attitude of the flexible guidance based on the principle that the potential energy stored in the system was the minimum at the equilibrium. Then the friction force was obtained according to the attitude of guide leaves and the moving velocity of the feed belt and the friction factor. Consequently, the load of the automatic feed mechanism can be calculated. Finally, an example was given to compute the load when the horizontal and elevating firing angles of the automation were respectively 45° and 30°. The computing result can be a criterion to determine the designing parameters of automat.
基金Project(51034009)supported by the National Natural Science Foundation of China
文摘A novel cooling system combining ultra fast cooling rigs with laminar cooling devices was investigated.Based on the different cooling mechanisms,a serial of mathematic models were established to describe the relationship between water flow and spraying pressure and the relationship between water spraying heat flux and layout of nozzles installed on the top and bottom cooling headers.Model parameters were validated by measured data.Heat transfer models including air convection model,heat radiation model and water cooling capacity model were detailedly introduced.In addition,effects on cooling capacity by water temperature and different valve patterns were also presented.Finally,the comparison results from UFC used or not have been provided with respect to temperature evolution and mechanical properties of Q235B steel grade with thickness of 7.8 mm.Since online application of the sophisticated CTC process control system based on these models,run-out table cooling control system has been running stably and reliably to produce resource-saving,low-cost steels with smaller grain size.
文摘文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比分析研究,数值模拟能够客观地反映起旋室旋流的流场特性,成果可为旋流溢洪道的研究应用提供参考.
文摘为探讨莱州湾生态系统年代际变化,基于莱州湾1980年代(1980s)和2020年代(2020s)相关数据,应用Ecopath with Ecosim(EwE)软件,分别构建莱州湾1980s和2020s的Ecopath模型,对比莱州湾生态系统年代际的结构和功能差异。结果显示,两个年代莱州湾生态系统均存在牧食食物链和碎屑食物链两种能量传递途径,能量流动主要集中在低营养级,能量流动规律符合金字塔逐级递减规律;与1980s相比,2020s莱州湾生态系统功能组营养级下降,生物量减少;2020s莱州湾流向碎屑量和系统总流量降低,资源再循环效率提高,总初级生产量/总呼吸量和系统净生产量降低,Finn’s循环指数和Finn’s平均路径长度增大,连接指数增大。研究表明,2020s莱州湾生态系统规模比1980s有所下降,生态系统的稳定性有所提高。
