海冰载荷作用下风力机抗冰锥体减载研究

提出了锥体抗冰结构来降低海冰对风力机结构的影响。以NREL 5 MW近海三叶片水平轴风力机为研究对象,基于Ralston算法建立冰载荷模型,采用开源多体动力学软件FAST计算塔架结构动力学响应,研究了不同锥角抗冰结构下塔顶位移和塔架载荷特性。结果表明:锥体结构能有效地缓解由海冰造成的危害,塔架剪切力、海冰载荷及塔顶位移随锥角的降低而减小,锥角由70°降至40°,海冰载荷降低55%~98%;安装锥体前后,塔架剪切力减小28.7%~58.9%,塔顶位移最多减小46%。     

地震及湍流风联合作用下的大型海上风力机结构动力学响应

为研究DTU 10MW近海桩柱式风力机塔架在地震激励下的动力学响应,基于p-y曲线法建立单桩基础与土壤的耦合模型,通过有限元软件ANSYS建立风力机塔架的有限元模型,分析不同速度湍流风和不同强度地震时塔架的瞬态动力学响应。结果表明:仅风载荷作用时,额定风速作用下塔架动力学响应明显高于切出风速;地震与风联合作用时,塔顶位移动态响应剧烈,但无明显规律;塔架加速度响应最大值位置约为四分之三塔高处,塔顶剪应力响应与地震持续时间有关。     

不同海况下近海超大型风力机动力学响应及结构损伤分析

以超大型DTU 10 MW单桩式近海风力机为研究对象,通过p-y曲线和非线性弹簧建立桩-土耦合模型,选取Kaimal风谱模型建立湍流风场,基于P-M谱定义不同频率波浪分布,并利用辐射/绕射理论计算波浪载荷,采用有限元方法对不同海况下单桩式风力机进行动力学响应、疲劳及屈曲分析。结果表明：不同海况波浪载荷作用下塔顶位移响应及等效应力峰值远小于风及风浪联合作用,其中风浪联合作用下风力机塔顶位移响应及等效应力略小于风载荷;波浪载荷对风载荷引起的单桩式风力机动力学响应具有一定抑制作用,此外相较于波浪载荷,风载荷为控制载荷;风载荷与风浪联合作用下风力机等效应力峰值位于塔顶与机舱连接处,波浪载荷风力机等效应力峰值位于支撑结构与桩基连接处;仅以风载荷预估风力机塔架疲劳寿命将导致预估不足;随着波浪载荷的增大,风力机失稳风险加大,波浪载荷不可忽略;不同海况下,风浪联合作用局部屈曲区域位于塔架中下端,在风力机抗风浪设计时,应重点关注此处;变桨效应可大幅降低风力机动力学响应、疲劳损伤及发生屈曲的风险。     

海冰载荷作用下海上风力机TMD减振研究

为保证桩柱式海上风力机塔架结构稳定和系统运行安全,提出安装于机舱内的调谐质量阻尼器(Tuned Mass Damper,TMD),以减弱海冰与湍流风联合作用环境下的风力机振动。基于多体动力学开源仿真软件(FAST),通过计算并分析NREL 5 MW海上风力机风-冰联合作用下塔顶振动特性,发现TMD控制对前后向的塔顶位移及塔基剪切力影响较小,但可以有效降低侧向的塔顶位移及塔基剪切力,降低幅度分别达39%与52%。同时,塔架一阶固有频率处的响应降低64%与90%,说明TMD装置能有效减弱风力机振动,保护风力机安全。     

基于土基-结构耦合作用的风力机塔架地震时频特性分析

为研究不同土质时地震载荷对大型风力机结构动力学响应的影响,基于Wolf方法建立风力机基础平台与土体的耦合模型,通过FAST软件仿真Wind PACT 1.5 MW风力机在不同土质和不同地震强度时塔架的动力学响应。通过分析不同工况下风力机的结构动力学响应,发现地震载荷对塔顶位移和塔基弯矩的影响不可忽略,尤其是塔顶侧向位移和塔基俯仰力矩。在九级设防烈度地震作用下,相比无地震工况,软土、硬黏土和岩土地质风力机塔顶侧向位移分别增大925%、785%和771%。且由于软土阻尼最小,能量耗散小,所以地震后塔架响应降低的速率最慢。     

高风速及风突变对风力机柔性部件振动特性研究

风力机运行在复杂多变的自然环境之中,风是影响风力机气动特性和振动特性的最直接因素,高风速及风速突变将诱发风力机更强的气动载荷。为探究风力机柔性部件在高风速及突变湍流风作用下的振动特性,以NREL(美国国家能源部可再生能源实验室)实测数据为湍流风数据源,并添加相干结构描述风速突变,以NREL 1.5 MW近海桩柱式风力机为样机,建立基于Kane方法的风力机结构动力学模型,并使用假设模态离散化方法对其进行柔性化,而后将该模型与风场和气动力模型一起组成气-弹相互耦合系统动力学模型,分别研究了风力机叶片和塔架的结构动力学响应。结果表明:相干结构的添加可使基础湍流风具有更大的风突变以及更高的湍流强度;额定风速附近,叶尖位移体现为挥舞,切出风速附近,叶尖位移同时体现为挥舞和摆振;相干结构的添加使得叶片和塔架振动加速度成倍增加。     

异步冰载荷作用下风力机动力学响应分析

为研究与结构接触表面不平整浮冰导致的冰激振动对风力机影响,建立风力机Kane多体动力学模型,采用异步Matlock模型模拟冰激振动,由Kaimal风速谱、指数风廓线模型和空间相干模型模拟来流风场,结合叶素动力学计算风力机非定常气动载荷,分析湍流风载荷和异步冰激振动模型作用下塔架动力学响应。研究结果表明：异步Matlock模型冰载荷峰值低于同步模型;塔顶前后位移受冰激振动影响较侧向更为显著,幅值和标准差均大幅提高;冰激振动导致塔顶前后位置破碎频率及其靠近叶片2阶挥舞频率倍频处幅值大幅提高,且异步Matlock增幅小于同步模型;异步Matlock模型对塔顶侧向位移影响较小。     

湍流风与浮冰联合作用下近海风力机动力学响应

以NREL 5 MW近海风力机为研究对象,基于Kaimal平稳随机风速谱模型建立风力机全域湍流风,同时采用Matlock模型计算动态冰力,模拟风力机所受冰激振动,研究在风-冰联合环境载荷作用下近海风力机动力学响应。结果表明:冰激振动极大地加剧塔顶各向振动;频域上,冰激振动影响主要集中于塔架1阶固有频率和叶片1阶摆振频率,且相应峰值与冰厚呈正相关关系;受冰激振动作用,塔架各向剪切力明显增加,且塔顶和塔基附近增幅大于塔身中部。     

多土层桩-土耦合效应对静止状态下近海超大型风力机地震动力学响应及屈曲的影响分析

以近海DTU 10 MW超大型风力机为研究对象,选用东海实测海床土壤参数构建桩周土水平抗力-桩基形变(p-y)曲线,并基于非线性弹簧单元建立纯砂土、纯黏土及多土层桩-土耦合效应模型,选取实测地震位移数据作为地震载荷,采用有限元方法对比研究了3种桩-土耦合效应下风力机动力学响应特性.结果 表明:多土层桩-土耦合效应下塔顶位移、塔顶前后位移及侧向位移峰值及其波动的剧烈程度小于纯砂土,但大于纯黏土,采用纯砂土或纯黏土构建桩-土耦合效应模型将导致预估响应结果不准确;不同桩-土耦合效应下,塔架一阶模态均被地震载荷诱发;地震作用时纯砂土桩-土耦合效应下塔架屈曲因子最小,多土层次之,纯黏土最大;塔架最大剪应力峰值位于塔架支撑结构处,地震作用时塔架下端易发生局部屈曲,结构设计时应重点关注此处.     

基于中国实测地震有效持续时间的风力机地震动力学研究

基于我国实测地震,对10 MW单桩陆上风力机在地震及湍流风载荷作用下的结构响应和局部损伤特性进行研究。采用阿里亚斯强度计算有效地震持续时间,从而对风力机进行时域分析。采用壳单元精细有限元模型,构建考虑湍流风、地震及土-构耦合效应的多物理场模型,开展10 MW单桩式陆上风力机的结构动力学研究。结果表明：湍流风载荷和地震载荷分别为影响风力机塔顶前后向位移和塔顶侧向位移的决定因素;地震载荷不同会导致地震诱导结构屈曲模态发生变化。     

风冰联合作用下大型单桩海上风电机组动力特性

考虑风荷载与冰荷载联合作用对大型单桩海上风电机组的影响,基于IEA 15 MW超大型单桩海上风电机组,采用一体化分析软件Openfast建立风冰联合作用下大型单桩耦合数值模型,开展超大型单桩海上风电机组在风冰联合作用下的动力响应分析。探究不同加载时长、冰激振动模型以及疲劳损伤组合方法对大型单桩海上风电机组的动力响应规律。计算结果显示：不同冰载数值计算模型塔基与泥面线载荷的计算结果差别较大,泥面线受冰荷载影响较大,同时泥面线位置较塔基位置承受更大的疲劳损伤,应重点关注。采用不同的荷载组合方向进行泥面线与塔基位置的疲劳损伤估计时,计算结果较风冰联合作用下疲劳损伤相对误差较大。因此,宜采用风冰联合加载的方法进行大型单桩海上风电机组的动力响应模拟,进而开展超大型单桩海上风电机组的疲劳损伤估计。     

基于流固耦合的风力机塔筒动态特性分析

塔筒动态特性分析对风力发电机的振动设计起着关键作用。文章以1.5 MW风力发电机塔筒为研究对象,将叶片旋转和随机风载荷作为载荷输入条件,建立风力机塔筒叶片旋转载荷模型、流固耦合风载荷模型、结构动力学方程,分析计算得到随机载荷下叶片旋转和风载共同作用时,风力机塔筒动态特性评估方法。     

Multidisciplinary design optimization of offshore wind turbines for minimum levelized cost of energy

This paper presents a method for multidisciplinary design optimization of offshore wind turbines at system level. The formulation and implementation that enable the integrated aerodynamic and structural design of the rotor and tower simultaneously are detailed. The objective function to be minimized is the levelized cost of energy. The model includes various design constraints: stresses, deflections, modal frequencies and fatigue limits along different stations of the blade and tower. The rotor design variables are: chord and twist distribution, blade length, rated rotational speed and structural thicknesses along the span. The tower design variables are: tower thickness and diameter distribution, as well as the tower height. For the other wind turbine components, a representative mass model is used to include their dynamic interactions in the system. To calculate the system costs, representative cost models of a wind turbine located in an offshore wind farm are used. To show the potential of the method and to verify its usefulness, the 5 MW NREL wind turbine is used as a case study. The result of the design optimization process shows 2.3% decrease in the levelized cost of energy for a representative Dutch site, while satisfying all the design constraints.     

考虑冲刷的单桩式海上风力机动力响应研究

为了研究复杂海洋环境下桩周冲刷对海上风力机动力响应的影响,以美国可再生能源实验室5 MW海上风力机为研究对象,建立风力机塔架-单桩-土体有限元模型,计入风浪和地震荷载对冲刷情况下的单桩式海上风力机进行动力响应研究。对比分析不同冲刷深度以及冲刷坡角对风力机系统固有频率和动力响应的影响。研究表明：当冲刷深度增加到二倍桩径时,风力机一阶固有频率降低至转子1P频率附近,容易引起共振;在风浪荷载以及风浪、地震联合荷载作用下,冲刷坡角不变,风力机最大位移与弯矩随着冲刷深度增加而增大,疏松土质条件下的增量大于紧密土;保持冲刷深度不变,冲刷坡角的变化对风力机动力响应影响较小。     

Wind turbine fatigue loads as a function of atmospheric conditions offshore

In recent years, there has been a growing interest by the wind energy community to assess the impact of atmospheric stability on wind turbine performance; however, up to now, typically, stability is considered in several distinct arbitrary stability classes. As a consequence, each stability class considered still covers a wide range of conditions. In this paper, wind turbine fatigue loads are studied as a function of atmospheric stability without a classification system, and instead, atmospheric conditions are described by a continuous joint probability distribution of wind speed and stability. Simulated fatigue loads based upon this joint probability distribution have been compared with two distinct different cases, one in which seven stability classes are adopted and one neglecting atmospheric stability by following International Electrotechnical Commission (IEC) standards. It is found that for the offshore site considered in this study, fatigue loads of the blade root, rotor and tower loads significantly increase if one follows the IEC standards (by up to 28% for the tower loads) and decrease if one considers several stability classes (by up to 13% for the tower loads). The substantial decrease found for the specific stability classes can be limited by considering one stability class that coincides with the mean stability of a given hub height wind speed. The difference in simulated fatigue loads by adopting distinct stability classes is primarily caused by neglecting strong unstable conditions for which relatively high fatigue loads occur. Combined, it is found that one has to carefully consider all stability conditions in wind turbine fatigue load simulations. Copyright © 2016 John Wiley & Sons, Ltd.     

Response analysis and comparison of a spar‐type floating offshore wind turbine and an onshore wind turbine under blade pitch controller faults

This paper analyses the effects of three pitch system faults on two classes of wind turbines, one is an onshore type and the other a floating offshore spar‐type wind turbine. A stuck blade pitch actuator, a fixed value fault and a bias fault in the blade pitch sensor are considered. The effects of these faults are investigated using short‐term extreme response analysis with the HAWC2 simulation tool. The main objectives of the paper are to investigate how the different faults affect the performance of wind turbines and which differences exist in the structural responses between onshore and floating offshore wind turbines. Several load cases are covered in a statistical analysis to show the effects of faults at different wind speeds and fault amplitudes. The severity of individual faults is categorized by the extreme values the faults have on structural loads. A pitch sensor stuck is determined as being the most severe case. Comparison between the effects on floating offshore and onshore wind turbines show that in the onshore case the tower, the yaw bearing and the shaft are subjected to the highest risk, whereas in the offshore case, the shaft is in this position. Copyright © 2014 John Wiley & Sons, Ltd.     

风浪入射角对漂浮式风力机动态响应影响研究

采用开源软件FAST并结合多体动力学方法,以驳船式(ITI Energy Barge)平台5 MW海上漂浮式风力机为研究对象,研究海上漂浮式风力机塔架与平台结构在风浪不同入射角下6个自由度大小与幅值变化,并分析风力机塔架与塔基在风浪入射角度不一致工况下的动态响应;将模拟所得数据在Matlab语言编辑的Mlife程序中运行,进而得到风力机等效疲劳载荷(DEL)。结果表明:平台6个自由度中,纵荡和纵摇随来流风速的变化最为显著;海上风力机的DEL不仅与风浪载荷大小有关,与其方向也有着密切关联;来流风、浪载荷之间的夹角较小时,风力机塔架和塔基的DEL相应较大。研究结果对海上Barge平台结构的设计与安装具有一定的参考价值。     

Predicting wind turbine blade loads and aeroelastic response using a coupled CFD–CSD method

The aeroelastic response and the airloads of horizontal-axis wind turbine rotor blades were numerically investigated using a coupled CFD–CSD method. The blade aerodynamic loads were obtained from a Navier–Stokes CFD flow solver based on unstructured meshes. The blade elastic deformation was calculated using a FEM-based CSD solver which employs a nonlinear coupled flap-lag-torsion beam theory. The coupling of the CFD and CSD solvers was accomplished in a loosely coupled manner by exchanging the information between the two solvers at infrequent intervals. At first, the present coupled CFD–CSD method was applied to the NREL 5MW reference wind turbine rotor under steady axial flow conditions, and the mean rotor loads and the static blade deformation were compared with other predicted results. Then, the unsteady blade aerodynamic loads and the dynamic blade response due to rotor shaft tilt and tower interference were investigated, along with the influence of the gravitational force. It was found that due to the aeroelastic blade deformation, the blade aerodynamic loads are significantly reduced, and the unsteady dynamic load behaviors are also changed, particularly by the torsional deformation. From the observation of the tower interference, it was also found that the aerodynamic loads are abruptly reduced as the blades pass by the tower, resulting in oscillatory blade deformation and vibratory loads, particularly in the flapwise direction.