东海某风场4MW风机塔筒结构疲劳特性

Fatigue Characteristics of 4 MW Wind Turbine Tower Structure in a Wind Farm in the East China Sea

海上风机塔筒长期受到风荷载等外部动力荷载作用,其应力响应相当不规则,容易发生疲劳破坏。由于每个风速工况出现的概率不同,而且塔筒在各工况下的响应也存在差异,因此有必要划分风速工况来编制疲劳应力谱。以东海某海上风电项目为例,建立塔筒结构三维精细化有限元模型,结合风速威布尔分布模型、雨流计数法和线性疲劳累积损伤法则,采用名义应力法计算塔筒的疲劳寿命,并与简化塔筒模型的计算结果进行对比分析,以期为风力机结构疲劳研究提供思路和参考。计算结果表明:通过划分风速工况来编制疲劳应力谱的方法是可行的;塔筒结构容易发生疲劳破坏的部位在塔筒中下部筒节之间的连接处及附近;在分析塔筒疲劳特性时采用壁厚随高度均匀变化的简化塔筒模型与精细化模型结果相差较大,会带来较大误差,因此建议建立精细化模型以合理预估风机塔筒疲劳寿命。

Due to the long-term external dynamic load,such as wind load,the tubular tower of an offshore wind turbine usually exhibits quite irregular stress responses,leading to fatigue failure.Considering the different probabilities of each wind speed condition and the different responses of the tubular tower under each condition,it is necessary to divide wind speed conditions into segments to compile the fatigue stress spectrum.A three-dimensional refined finite element model of the tubular tower structure was established based on an offshore wind power project in the East China Sea.Combined with the Weibull distribution model of wind speed,the rain-flow counting method,and the linear fatigue cumulative damage law,the nominal stress method was used to calculate the fatigue life of the tubular tower.At the same time,the simplified tubular tower model was established and compared with the refined model,so as to provide ideas and references for the fatigue research of the wind turbine structure.The calculation results show that it is feasible to compile the fatigue stress spectrum by dividing wind speed conditions.The parts prone to fatigue damage are located at or near the junctions between the tower segments in the middle and lower part of the tubular tower.In the analysis of the fatigue characteristics of the tubular tower,the results of the simplified tubular tower model whose wall thickness changes uniformly with the height and the refined model are quite different,which will cause large errors.Therefore,it is recommended to establish a refined model to reasonably predict the fatigue life of the tubular tower.