In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding(P-FCAW) process in the horizontal...In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding(P-FCAW) process in the horizontal position. The results indicate the presence of a stable ‘‘flux pole'' during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this ‘‘flux pole'' was beneficial for droplet transfer in the‘‘axial droplet transfer'' mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter,rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position.展开更多
This paper theoretically investigates the dependence of leaky mode coupling between inner core fundamental mode and outer core defect mode on phase and loss matching in pure silica dual-core photonic crystal fibres wi...This paper theoretically investigates the dependence of leaky mode coupling between inner core fundamental mode and outer core defect mode on phase and loss matching in pure silica dual-core photonic crystal fibres with the multi-pole method. The complete mode coupling can take place when both the phase and loss matching conditions are satisfied at the avoided anti-crossing wavelength. It shows the influences of cladding structure parameters including the diameters of cladding air holes d1, diameters of outer core holes d2 and hole to hole pitch A on the characteristics of leaky modes coupling. The coupled-mode theory is used to analyse the mode transition characteristics and the complete coupling can be clearly indicated by comparing the real and imaginary parts of propagation constant of the leaky modes.展开更多
基于高温超导(High Temperature Superconductivity,HTS)直流感应加热技术加热质量好、加热效率高等优点,提出一种基于圆筒形多极直流电机结构的对极铁芯高温超导直流感应加热装置.首先,针对加热装置气隙磁场与铝棒温升特性,采用麦克斯...基于高温超导(High Temperature Superconductivity,HTS)直流感应加热技术加热质量好、加热效率高等优点,提出一种基于圆筒形多极直流电机结构的对极铁芯高温超导直流感应加热装置.首先,针对加热装置气隙磁场与铝棒温升特性,采用麦克斯韦方程组与法拉第电磁感应定律,并结合固体热传导方程,建立铝棒加热过程数值模型;其次,兼顾加热装置环形铁芯与直流电机多极结构模式,构建4极与2极电磁模型与热模型;再次,针对铝棒电导率、转速以及长度对铝棒加热过程的影响,利用对极加热装置电磁热模型,研究铝棒内涡流与加热功率的变化过程;最后,针对加热区域磁场强度不足的问题,基于直流电机极靴长度对气隙磁场大小的影响,提出极靴结构改善气隙磁场模型.研究结果表明:2极铁芯结构下铝棒最大磁通密度高于4极结构0.16 T,铝棒最大温度高于4极结构54 K;铝棒内涡流密度和加热功率与铝棒电导率、长度以及转速呈正相关性;极靴结构提高了铝棒磁通密度0.11 T,铝棒温度提升了4.2℃.展开更多
以10 k W·h飞轮储能系统的电磁轴承为对象,分析了E型12极径向电磁轴承的动态载荷特性。通过电磁轴承动态载荷区图,建立了转子不平衡激励载荷与动态载荷区的联系,以提高最大承载能力为目标,合理匹配了电磁轴承磁铁与功率放大器组合...以10 k W·h飞轮储能系统的电磁轴承为对象,分析了E型12极径向电磁轴承的动态载荷特性。通过电磁轴承动态载荷区图,建立了转子不平衡激励载荷与动态载荷区的联系,以提高最大承载能力为目标,合理匹配了电磁轴承磁铁与功率放大器组合。确定了执行器的主要技术参数和转子动平衡精度等级,为磁悬浮储能飞轮系统总体设计、电磁轴承系统设计提供了设计方法和理论依据。展开更多
文摘In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding(P-FCAW) process in the horizontal position. The results indicate the presence of a stable ‘‘flux pole'' during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this ‘‘flux pole'' was beneficial for droplet transfer in the‘‘axial droplet transfer'' mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter,rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position.
基金Project supported by the National Key Basic Research Special Foundation of China (Grant No. 2010CB327605)the National High-Technology Research and Development Program of China (Grant No. 2009AA01Z220)+2 种基金the Key Grant of the Chinese Ministry of Education (Grant No. 109015)the Discipline Co-construction Project of Beijing Municipal Commission of Education (Grant No. YB20081001301)the Open Fund of Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education,and the Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications (Grant No. CX201023)
文摘This paper theoretically investigates the dependence of leaky mode coupling between inner core fundamental mode and outer core defect mode on phase and loss matching in pure silica dual-core photonic crystal fibres with the multi-pole method. The complete mode coupling can take place when both the phase and loss matching conditions are satisfied at the avoided anti-crossing wavelength. It shows the influences of cladding structure parameters including the diameters of cladding air holes d1, diameters of outer core holes d2 and hole to hole pitch A on the characteristics of leaky modes coupling. The coupled-mode theory is used to analyse the mode transition characteristics and the complete coupling can be clearly indicated by comparing the real and imaginary parts of propagation constant of the leaky modes.
文摘以10 k W·h飞轮储能系统的电磁轴承为对象,分析了E型12极径向电磁轴承的动态载荷特性。通过电磁轴承动态载荷区图,建立了转子不平衡激励载荷与动态载荷区的联系,以提高最大承载能力为目标,合理匹配了电磁轴承磁铁与功率放大器组合。确定了执行器的主要技术参数和转子动平衡精度等级,为磁悬浮储能飞轮系统总体设计、电磁轴承系统设计提供了设计方法和理论依据。
