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活塞风对接触线的影响研究
Study of the Piston Wind on Contact Line
【作者】 陈荣；
【导师】 王国志；
【作者基本信息】 西南交通大学 ， 机械电子工程， 2013， 硕士
【摘要】 兰新线沿路气候、地形极其复杂,隧道是兰新铁路的重要组成部分,隧道共计33座,总延长11.8公里。列车在隧道内运行时,产生活塞风,而接触网系统对风载荷作用敏感。由于隧道特殊的环境位置,不方便了解列车在隧道中的运行状况。此外,隧道内接触网的检修工作也较明线上困难。因而研究活塞风形成机理、流场特性及活塞风对接触网的影响情况具有很重大的现实意义。本课题源自铁道部对兰新铁路的电气化改造重点项目(2008J019)。本文运用了理论公式推导与数值模拟相结合的方法,研究了活塞风形成机理。从理论上,基于恒定流伯努利方程,推导得出活塞风风速的计算公式,得出影响活塞风的各因素,并定性地分析了各因素对活塞风的影响情况。在不同的环境条件下,利用流体分析软件Star-CD,建立了列车过隧道的横截面动网格模型。研究分析了活塞风风速及风压,验证了隧道内活塞风最大风速在列车尾流中形成、列车头部出现正压、尾部出现负压等结论,通过比较,结果表明列车运行速度对活塞风风速的影响最大。在接触网系统中,接触线的刚性最小,所以在研究活塞风对接触网系统的影响时,主要分析了活塞风引起的接触线的偏移量。在不同的列车运行速度及列车外形等环境条件下,建立了列车过隧道的纵截面动网格模型。在钝形列车尾流中形成了一个完整且明显的漩涡,更容易将物体卷入其中。流线型列车在降低活塞风的不良影响上有很大的优势。通过分析接触线高度处的流场,得出在列车进出隧道的整个过程中,接触线高度处的活塞风风速沿隧道高度方向(Z轴)的分量Vz,在隧道入口处有最大值。利用有限元分析软件ANSYS,建立隧道内接触网模型。将风速转化为作用力,加载到接触线节点上,计算活塞风引起的接触线的偏移量。建立列车过隧道的三维模型,对计算机的性能要求很高。在计算机能够实现的前提下,优化计算参数。在建立三维动网格模型时,在软件ANSYS ICEM里进行网格的划分,再将模型导入到Star-CD软件中进行计算。对三维模型的流场进行分析,得出接触线位置处,沿隧道宽度方向的风速Vy很小,可以忽略不计。同样,取出三维模型中的流场参数,作用到接触网模型中,研究活塞风对接触线的影响情况。综合分析比较二维、三维模型,为实际工程研究提供一定的参考。
【Abstract】 The climate and topography along the Lanxin railway is very complicated. Tunnels are important parts of the railway. There are totally33tunnels, which are about eleven point eight kilometers. When the train passes through a tunnel, there will produce piston wind. Then, the contact system is sensitive to wind load. Due to the special environment of tunnel, it is not convenient to know the situation when the train passing through a tunnel. In addition, the repairing work in tunnel is more difficult than in open line. Therefore, the study about formation mechanism of piston wind, the flow field characteristics and the influence of the piston wind on contact system has very important significance. This topic is the key project of electrification transformation to Lanxin railway from the ministry of railways (2008J019).The article combines two methods of theory formula deduction and numerical simulation in the research of the piston wind’s formation mechanism. The calculation formula in theory and influence factors of the piston wind is obtained based on the constant flow’s Bernoulli equation. Besides, the influence is qualitatively analyzed. With the fluid analysis software Star-CD, the cross section of a dynamic grid model is established in different speed of trains, different blockage ratio, different length of trains, and different length of tunnels. The speed of the piston wind and the pressure in tunnel is analyzed. It is verified that the maximum speed of the piston is formed in train rear, train head appears positive pressure, and train rear appears negative pressure. Through the comparison, the train’s speed has the biggest influence on the piston wind.In the contact system, the contact line’s stiffness is the smallest. So, in research of the influence of the piston wind on contact system, the contact line’s offset is mainly taken in account. The longitudinal section of the dynamic mesh model is established in different speed and shape of train. A complete and clear vortex is formed in rear of blunt-shaped train, in which the objects are more easily involved. The streamlined train has a lot of advantages in reducing the harmful effects of the piston wind. Through the analysis of flow field in contact line’s height, it is concluded that the maximum speed of piston wind along the tunnel’s height direction is at tunnel’s entrance. The model of contact system in the tunnel is established with the finite element analysis software ANSYS. The speed of wind is changed into force, which is loaded to nodes of the contact line. The offset of the contact line will be gained. In order to build3D model of the train passing through a tunnel, the computer should has high performance. The parameters of model will be optimized in order that the computer can realized. The grids are divided in the software ANSYS ICEM. Then, the model will be imported into the software Star-CD and calculated. The speed of wind at the height of contact line along the direction of tunnel’s width is very small and can be neglected. With the same method, the research of the three dimension model will be carried on. It is necessary to compare two dimension and three dimension model, which will provide certain reference to practical engineering.