车顶绝缘子气流分布及背风面重污区面积占比分析

Analysis on airflow distribution of roof insulators and proportion of heavily polluted areas on leeward side

随着高速列车运行速度的不断提升,车顶绝缘子的气流分布也变得复杂,而气流分布与污秽沉积密切相关,且高速气流下绝缘子背风面形成重污秽区,该区域形状及面积占比直接影响绝缘子的闪络特性。为探究车顶绝缘子气流分布及背风面重污秽区域面积占比,采用欧拉双流体模型建立绝缘子积污仿真模型,计算车顶绝缘子外部流场分布,分析绝缘子表面污秽不均匀分布的成因,并且以绝缘子芯棒周向静压为基础,提出基于压力最低点和边界层分离点的背风面重污秽区面积占比计算方法,最后通过风洞试验验证此方法的有效性。研究结果表明:绝缘子周围气流速度呈现明显的分区,绝缘子后方尾流区内断面的Z向速度由“U型—W型—V型—U型”向平稳区过渡;而绝缘子前方断面的Z向速度由“U型—V型—U型”向平稳区过渡;57 m/s正向来流下绝缘子表面污秽呈不均匀分布,背风面处有类似梯形的低速积污区存在,基于压力最低点求出的重污秽区域面积占比比基于边界层分离点的对应数值略大,差值在4.43%~7.64%之间,二者结果与实验值的相对误差分别在−1.1%~−18.7%和9.5%~24.1%之间。研究结果可为优化设计车顶绝缘子结构及优化车顶装置的布局提供参考。

With the continuous increase of the high-speed train operation speed,the airflow distribution of the roof insulator also becomes complicated,and the airflow distribution is closely related to the pollution deposition.Moreover,under the high-speed airflow,the leeward surface of the insulator forms a heavily polluted area,and the shape and area proportion of this area will directly affect the flashover characteristics of the insulator.In order to explore the airflow distribution of roof insulator and the area proportion of heavily polluted area on the leeward surface,the Eulerian two-fluid model was used to establish a simulation model the insulator contamination.This paper calculated the external flow field distribution of roof insulators,analyzed the causes of uneven distribution of insulator surface fouling,and proposed a method to calculate the area proportion of heavily fouled area on the leeward side based on the pressure nadir and boundary layer separation point based on the circumferential static pressure of the insulator mandrel,and finally verified the effectiveness of this method through wind tunnel tests.The research results are drawn as follows.The airflow velocity around the insulator presents obvious zoning phenomenon,and the Z-directional velocity of the section in the tail flow area behind the insulator transitions from“U-type-W-type-V-type-U-type”to the smooth area.While the Z-directional velocity of the section in front of the insulator transitions from“U-type-V-type-U-type”to the smooth area.The fouling on the insulator surface under the 57 m/s forward incoming flow is unevenly distributed,and a trapezoidal like low-velocity fouling area exists at the leeward side.The area of the heavy fouling area based on the pressure nadir is slightly larger than the corresponding value based on the boundary layer separation point,with a difference between 4.43%and 7.64%,the relative errors between the two results and the experimental values ranged from-2.9%to-20.4%and 8.7%to 22.69%,respectively.The study results can provide a reference for optimizing the design of the roof insulator structure and optimizing the layout of the roof unit.