【作者】 刘贻雄；

【导师】 杨从新；

【作者基本信息】 兰州理工大学 ， 流体机械及工程， 2012， 硕士

【摘要】 现代大型风力机塔架采用薄壳型筒状高耸结构（以下简称塔筒），高度近100m，底部直径在5m以上，壁厚不到直径的1/100，属于典型的细长薄壳结构。塔筒底端固定，顶端自由且承受机舱和风轮的重力和气动载荷，该结构形式容易发生振动和失稳。随着机组的单机容量不断增大，重量和外型尺寸随之增大，塔筒的高度也随之增加，作用在塔筒上的重力载荷和气动载荷交变性和时变性更加显著。近年来，塔筒在风电机组运行过程中倒塌或失稳的事故时有发生。因此，塔筒结构动力学和稳定性研究对风电机组的可靠性和安全性至关重要。本文以某2.5MW风力机塔筒(φ5.8m×φ3.2m×95.2m)为研究对象，运用理论分析和数值模拟方法研究了塔筒的动力学特性、疲劳、屈曲稳定性。考虑到风是风力机机组运行过程中主要的载荷源，由风产生的气动载荷是塔筒动力响应、疲劳和屈曲稳定性的直接原因。首先，参照IEC标准对风况及风速分布进行理论分析，并借助风力机专门软件GH Bladed模拟风速的概率分布以及风湍流分布情况；其次，从理论上分析了机组各部件的载荷，主要是风轮所受的气动载荷，参照德国劳埃德船级社规范（GL2010）和Bladed原理手册，运用风力机专门软件GH Bladed模拟机组在各种工况（启动、正常发电、紧急刹车、停机等）下的载荷，并将气动载荷通过坐标变换等效转换到塔筒顶端；最后，将模拟所得到的载荷施加到ANSYS塔筒分析模型上进行动力学及动态响应分析、疲劳分析和屈曲稳定性分析。在研究过程中，得出了一些结论，总结如下：（1）在风力机塔筒的结构动力响应中，低阶模态占主要地位，高阶模态对响应的贡献很小，阶数越高，其贡献就越小。而且，由于结构阻尼的作用，响应中的高阶部分衰减也很快，故高阶模态可以忽略不计；（2）塔筒顶端机舱和风轮的总质量对塔筒的弯曲振动频率有较大影响，塔筒的振动频率随顶端质量的增大显著降低；（3）塔筒在机组运行过程伴随着瞬态动力学响应过程，来自风速变化和运行工况下的动载荷对塔筒产生巨大的瞬态应力和变形，其瞬时值远大于响应的叠加值，对塔筒产生瞬时冲击，易造成塔筒损坏；（4）在切出风速和额定风速条件下，塔筒损伤阵列主要集中在低应力副区域，不足以造成塔筒的失效；而在极限风速（70m/s）条件下，塔筒在高应力副区损伤较大，对塔筒的产生损伤破坏；（5）轴压载荷以及风轮传递给塔筒的横向载荷对塔筒的屈曲失稳起主要作用；塔筒为缺陷敏感型结构，底部开设门洞塔筒的屈曲性能有很大影响，相同载荷情况下，圆弧形门洞比矩形门洞有更好的屈曲性能；沿门洞边缘添加门框有助于提高塔筒的屈曲强度。本文从理论上对风力机组载荷进行了分析，并运用风力机专业软件Bladed对机组载荷的进行了模拟，获取了运行工况下的载荷。塔筒在典型工况下的动态响应表明塔筒在动力响应过程中的应力应变在材料的许可范围之内；塔筒的屈曲分析表明塔筒满足屈曲强度要求；不同风速工况下的疲劳分析表明塔筒的疲劳寿命满足设计寿命。更多还原

【Abstract】 High-rise thin-shell tube structure is adoptted on modern large-scale wind turbine tower(hereinafter referred to as tower); the height is nearly100m, the bottom diameter beyond5m and the wall thickness less than1/100compared diameter, which belongs to typicalslender shell structure. For constraints boundary conditions, tower is fixed at the bottom,the top is free and bear loads form gravity and aerodynamic of nacelle and rotor, which isprone to cause vibration and instability. With increase of power capacity of wind turbine,the mass and geometric dimension of wind turbine are increasing, the height of tower isalso increasing, therefore, the gravity loads and aerodynamic loads on the tower are morevariable. In recent years, the accident of tower falling down as instability and bucklinghappened sometimes during operation. Therefore, the structural dynamic response andstability on tower are essential to wind turbine’s reliability and security.A2.5MW wind turbine tower is adopted as subject in this study. Theoretical analysisand numerical simulation method are used to study tower structure dynamic, fatigue andbuckling stability. Considering the wind is main source load during the operation of windturbine, aerodynamic load generated by wind is the direct cause of tower dynamicresponse, fatigue and buckling stability. First, the wind conditions and wind speeddistribution are analyzed in theoretical method refer to IEC standard, and wind speedprobability distribution and wind turbulence distribution are simulated in specializedwind turbine software-GH Bladed. Second, the loads of wind turbine components areanalyzed theoretically. According to German Lloyd (GL2010) and Bladed manualprinciple, the running loads under operating conditions (such as start, normal powergeneration, emergency brake, stopping, etc.) are simulated in GH Bladed，and theaerodynamic loads are transfer equivalently to the top of tower through coordinatetransformation matrix. Finally, tower dynamic response, fatigue and buckling stability areanalyzed in theory and simulated in ANSYS software. In the course of this study, someconclusions are summarized as follows:(1) In structural dynamic response of wind turbine tower, lower modal dominateresponse and contribution of higher modal is very tiny. Moreover, since the role ofstructural damping, high-level part of response decays quickly which is negligible.(2) Total gravity of nacelle and rotor on the top of tower has great impact on thefrequency of bending vibration, and the vibration frequency of tower is significantlyreduced with increase of gravity. (3) Tower accompanied by transient dynamic response during wind turbine operating;dynamic load on tower from wind and operating conditions produce large transient stressand deformation, and its instantaneous value is much larger than response superpositionvalue which cause instantaneous impact damage on tower.(4) In cut-out speed and rated wind speed, the tower damage array mainly happens inlow stress area which is not enough to cause the failure of tower; in limit wind speed, thedamage of tower happens in high-stress district which is damage to tower.(5) Axial compression load and lateral load of tower play a major role in towerbuckling. Tower tube is defect-sensitive structure, and opening at the bottom of towerhave significant impact on tower buckling. In the same load case, arc-shaped opening hasbetter buckling performance than rectangular opening.The frame along door edge ishelpful to improve tower buckling strength.In this paper, the loads of wind turbine are analyzed in theory, and running loads aregot by simulation in Bladed. The dynamic response of tower in typical operatingcondition shows that stress and strain meet the material mechanical scope; tower bucklinganalysis shows that tower buckling strength meets safety requirement; the fatigueanalysis in different wind speed conditions show that tower fatigue life satisfyrequirement of design life.更多还原