为研究兰新高铁大风区段挡风墙对接触网正馈线气动特性的影响,基于流体力学建立正馈线流场模型,分别针对无墙和有墙的情况,分析正馈线在不同风速下气动特性的变化规律。研究结果表明:挡风墙对气流有较强的汇聚作用,大幅增加了正馈线周...为研究兰新高铁大风区段挡风墙对接触网正馈线气动特性的影响,基于流体力学建立正馈线流场模型,分别针对无墙和有墙的情况,分析正馈线在不同风速下气动特性的变化规律。研究结果表明:挡风墙对气流有较强的汇聚作用,大幅增加了正馈线周围的空气流动速度。随着来风速度的增大,挡风墙后正馈线处风攻角也随之增大,当风速达到15 m/s 及以上时,攻角基本稳定在29°~30°之间。有墙条件下正馈线升力及阻力系数幅值加大且呈现无规律振荡,挡风墙对正馈线气动力的增大效应是导致正馈线发生低频高幅舞动的主要原因。挡风墙外形尺寸对于正馈线气动特性有重要影响,选择合适的高度和截面宽度可一定程度改善正馈线气动特性,以减少舞动的发生。展开更多
针对视频监测得到铁路接触网图像背景复杂、目标细弱而使电力线提取困难、效率降低的问题,提出一种结合背景特征和改进Ratio算子的区域链码(Ratio-based background features and chain code tracking,RBCT)电力线提取方法。首先,分析...针对视频监测得到铁路接触网图像背景复杂、目标细弱而使电力线提取困难、效率降低的问题,提出一种结合背景特征和改进Ratio算子的区域链码(Ratio-based background features and chain code tracking,RBCT)电力线提取方法。首先,分析接触网电力线图像背景特征,对不同类别背景图像进行灰度值分析、预处理加强来消除背景噪声并增强电力线目标。然后,利用分析得到的线特征检测阈值进行边缘检测,对电力线目标边缘做Ratio算子处理。最后,对检测得到目标边缘进行四方向链码聚类分析,识别电力线目标。结果表明,相比传统Canny、Ratio边缘提取方法,所提方法具有良好的抗噪能力和更高的电力线识别精确度。算法能够消除边缘检测出现的噪声,解决电力线检测中出现的断股、分裂问题,可准确完整地提取不同种类复杂背景下的电力线目标,具有较高工程应用价值。展开更多
The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-po...The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-porcelain insulator is designed.A multi-physics coupling simulation model is built based on numerical simulation methods of the electromagnetic field theory and computational fluid dynamics.Taking average electric field intensity on the surface of the insulator as the characteristic parameter of the electric field distortion degree and the snow crystal collision coefficient and distribution coefficient as the characteristic parameter of snow crystal deposition,the characteristics of snow crystal deposition under different wind speeds and wind direction angles and the electric field characteristics under two snow cover types are analyzed.The simulation results show that the average electric field intensity of composite-porcelain insulators is 10.4%and 13.8%,respectively,lower than that of porcelain insulators in vertical and horizontal wind snow covers,which can effectively reduce the degree of electric field distortion.The collision coefficient of snow crystals on the surface of the composite-porcelain insulator sheds is 16.0%higher than that of the porcelain insulator,and the collision coefficient of the trunk and the fittings are lower 20.2%and 11.9%than that of the porcelain insulator.There is almost no change in the distribution coefficient of the insulator sheds.展开更多
文摘为研究兰新高铁大风区段挡风墙对接触网正馈线气动特性的影响,基于流体力学建立正馈线流场模型,分别针对无墙和有墙的情况,分析正馈线在不同风速下气动特性的变化规律。研究结果表明:挡风墙对气流有较强的汇聚作用,大幅增加了正馈线周围的空气流动速度。随着来风速度的增大,挡风墙后正馈线处风攻角也随之增大,当风速达到15 m/s 及以上时,攻角基本稳定在29°~30°之间。有墙条件下正馈线升力及阻力系数幅值加大且呈现无规律振荡,挡风墙对正馈线气动力的增大效应是导致正馈线发生低频高幅舞动的主要原因。挡风墙外形尺寸对于正馈线气动特性有重要影响,选择合适的高度和截面宽度可一定程度改善正馈线气动特性,以减少舞动的发生。
文摘针对视频监测得到铁路接触网图像背景复杂、目标细弱而使电力线提取困难、效率降低的问题,提出一种结合背景特征和改进Ratio算子的区域链码(Ratio-based background features and chain code tracking,RBCT)电力线提取方法。首先,分析接触网电力线图像背景特征,对不同类别背景图像进行灰度值分析、预处理加强来消除背景噪声并增强电力线目标。然后,利用分析得到的线特征检测阈值进行边缘检测,对电力线目标边缘做Ratio算子处理。最后,对检测得到目标边缘进行四方向链码聚类分析,识别电力线目标。结果表明,相比传统Canny、Ratio边缘提取方法,所提方法具有良好的抗噪能力和更高的电力线识别精确度。算法能够消除边缘检测出现的噪声,解决电力线检测中出现的断股、分裂问题,可准确完整地提取不同种类复杂背景下的电力线目标,具有较高工程应用价值。
基金National Natural Science Foundation of China(No.51867013)。
文摘The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-porcelain insulator is designed.A multi-physics coupling simulation model is built based on numerical simulation methods of the electromagnetic field theory and computational fluid dynamics.Taking average electric field intensity on the surface of the insulator as the characteristic parameter of the electric field distortion degree and the snow crystal collision coefficient and distribution coefficient as the characteristic parameter of snow crystal deposition,the characteristics of snow crystal deposition under different wind speeds and wind direction angles and the electric field characteristics under two snow cover types are analyzed.The simulation results show that the average electric field intensity of composite-porcelain insulators is 10.4%and 13.8%,respectively,lower than that of porcelain insulators in vertical and horizontal wind snow covers,which can effectively reduce the degree of electric field distortion.The collision coefficient of snow crystals on the surface of the composite-porcelain insulator sheds is 16.0%higher than that of the porcelain insulator,and the collision coefficient of the trunk and the fittings are lower 20.2%and 11.9%than that of the porcelain insulator.There is almost no change in the distribution coefficient of the insulator sheds.
