输电导线覆冰生长及影响因素数值分析模型

Numerical Simulation for Icing and Influence on Transmission Line

针对现有输电线路覆冰生长模型仅注重覆冰生长量、难于准确预测覆冰形貌的问题,建立了输电导线局部冰层增长计算模型。采用空气动力学方程求解覆冰导线周围气流场参数、覆冰表面对流换热系数,进而采用欧拉二相流模型计算覆冰导线表面过冷却液滴碰撞系数;建立包含液滴碰撞、溢流、蒸发、升华等因素的质量平衡方程,基于此方程推导出计算对象热量平衡方程,并采用多级假设、一维搜索求解方程中多个未知量,得出各单元的冻结系数和覆冰质量。算例表明:局部碰撞系数及碰撞区域随风速的提高快速增大,覆冰量相应增大;而环境温度及导线电流的增加使得溢流水出现,覆冰类型由雾凇向雨凇过渡;模型所得覆冰形貌和覆冰量与已有实验结果基本相符,计算结果满足电力系统工程需要。

The existing transmission line ice growth models only focus on the ice mass, it is difficult for them to predict ice morphology accurately. A computational model for local ice accretion on transmission lines is established in this study. Air dynamics equation is considered to solve parameters of the flow field around conductor, then Eulerian two-phase model is chosen to calculate droplet collision coefficient on the surface of iced conductor. Mass balance equation, including the parameters of droplet collision, water runback, evaporation and sublimation, is established, then icing heat balance equation is constructed. All unknown variables in the model are acquired by one-dimensional search under multiple hypothesis, and the freeze coefficient and ice mass of each unit are obtained. Eventually, the cases show that the local droplet collision coefficient and collision area increase with wind speed; rising temperature and conductor current leads to the water runback to transform rime ice type to glaze ice type. The obtained icing morphology and weight coincide well with the existing experimental results.