雷击电弧气爆效应对风机的损伤机制与叶片优化设计

Damage Mechanism of Wind Turbine Under the Effect of Gas Burst Caused by Lighting Induced Arc and Optimized Design of the Turbine Blade

风机叶片雷击灾害事故频发,而雷击电弧对叶片气爆损伤机制尚不清晰,传统实验手段难以测量损伤过程中的细节参数。因此,以实际风机叶片为基础,搭建雷击电弧路径几何模型。基于磁流体动力学理论,利用有限元仿真软件COMSOL分别探究温度和压力在叶片内部的分布情况。进一步,对比不同引弧方式和雷击点位置对叶片材料碳化程度和后缘压力最大值的影响作用。发现叶片在遭受雷击后,雷击点的温度先迅速升高至最大值,然后缓慢降低,高温区域主要分布在雷击电弧周围。叶片后缘的压力先增加至峰值,然后呈现震荡衰减趋势。高压力区域先分布在右侧腹板与后缘之间,后逐渐向整个叶腔内扩散。叶片材料碳化程度和后缘压力最大值与已有文献的实验结果较为吻合,验证了仿真模型的正确性。当雷击点靠近叶尖时,叶片材料碳化程度和后缘压力最大值呈现上升趋势,当引下线布置于主梁时,上述两者均低于引下线布置于右侧腹板的情况。最后,从防雷角度出发,建议将引下线布置于主梁,同时使用环氧树脂将叶片后缘粘接处浇铸成半径为30mm的圆角。

Nowadays, many wind turbine blades are hit by lightning. But it is still unclear for the mechanism of gas burst damage caused by lightning arc and hard to measure relevant parameters during the damage process through traditional experimental methods. Hence, this paper establishes a lightning arc geometry model with reference to real blades. Based on magneto hydrodynamics theory, finite element simulation software COMSOL was used to investigate the distribution of temperature and pressure inside the blade. Furthermore, we analyzed the influence of different arc ignited methods and lightning strike positions on the carbonization degree of blade materials and the maximum pressure at the trailing edge. It is found that after suffering lightning strike, the temperature at lighting strike point increases steeply to maximum, then decreases slowly, and the high temperature area mainly distributes around the arc path. The pressure at the trailing edge first rises to the peak value and then shows a trend of turbulent decrease. High pressure area first distributes between the right web and trailing edge and then gradually spreads into whole blade cavity. Blade carbonization degree and the maximum pressure at trailing edge match the experimental results of previous literatures, which verify the correctness of simulation model. When lightning strike point is closer to the tip of blade, blade’s carbonization degree is more severe and so is the trailing edge’s maximum pressure. When the down-conductor is set on the main beam, the above two parameters are smaller than that when set on the right web. Finally, from the perspective of lightning protection, the authors suggest setting the down-conductor on the main beam, meanwhile using epoxy resin to cast the trailing edge into a rounded corner with the radius of 30 mm.