大型风力机叶片模态测试与分析

利用建成的大型风力机叶片的振动特性分析装置,用测力法和不测力法对风力机叶片进行模态试验及分析,测试了风力机叶片的模态参数（固有频率、阻尼和振型）,得到了叶片的振动特性。采用共振法将偏心电机和变频器连成一体作为激励源测试了叶片的固有频率,实验验证了单叶片的危险运行频率。对大型风力机叶片模态试验及分析提供了可靠的实验装置和试验方法,对风力机叶片动力学特性分析提供有力工具。     

风力机叶片动力特性实验台设计

设计开发了一种风力机叶片动力学特性实验台,可以进行风力机叶片的静载荷实验、模态测试、叶片损伤测试、模拟桨叶结冰附着物载荷实验、桨叶疲劳载荷实验以及破坏性实验等。介绍了实验台的设备组成、结构特点以及该实验台的主要功能,在实验台上进行了风力机叶片的静态载荷实验和模态测试,得出了实验用风力机叶片的六阶模态参数,利用MAC、MOV两种模态判定准则对试验结果进行了验证。     

钝尾缘叶片有限元模态与实验模态的对比研究

风力机叶片的模态分析是保障风力机整机稳定性及其可靠性分析的重要基础。对中国科学院工程热物理研究所研发的100kW钝尾缘实验叶片进行了有限元模态及实验模态研究,得出了叶片前几阶模态的振型及频率,探讨了对叶片稳定性影响比较显著的模态特性,通过对有限元模态及实验模态结果对比,分析了产生误差的原因及产生共振的可能性,为风力机叶片的稳定运行提供了理论依据。     

风力机预弯叶片结构与静气弹性参数化有限元分析方法研究

构建了风力机预弯叶片气动外形和铺层结构的参数化表达模型,采用MATLAB与ANSYS APDL相结合的方法对复合材料预弯叶片进行参数化有限元建模、加载和结构分析,并以某1.5 MW预弯叶片为例验证了该方法的正确性;基于修正的叶素动量理论和气动载荷参数化分布加载方法,对风力机预弯叶片的静气弹性进行分析和研究,结果表明预弯叶片的展向变形有助于叶片气动功率的提高,而叶片扭转变形造成风力机实际气动功率的降低,根据叶片的计算扭转变形,在叶片的设计中增大叶片的预扭转角度可避免叶片因弹性扭转变形造成的设计功率偏离。研制了风力机叶片结构性能和静气弹性分析工具(WTBSA),为预弯叶片的多学科优化设计奠定了基础。     

直线翼垂直轴风力机起动性的实验研究

为探明直线翼垂直轴风力机的叶片个数对其起动性的影响,设计制作了可更换叶片个数(1～5枚)的风力机模型,通过风洞实验获得了起动力矩与转角的关系曲线,并与用单叶片力矩模拟的结果进行了对比。接着又制作了1台3叶片小型风力机模型,进行了烟线法可视化实验,获得了不同转角下的风力机周围流场迹线图。两项实验结果表明:增加叶片个数可使风力机平均起动性提高,但叶片间相互影响也增加,不同角度下各叶片周围流场受影响程度不同,对叶片受力和风力机起动力矩的影响程度和趋势也不同。     

预弯对10MW级风力机叶片气动特性的影响

为分析预弯处理对10 MW级风力机叶片气动特性的影响,以DTU 10 MW风力机为例,采用CFD数值模拟方法,研究均匀来流不同风速下风力机的输出功率,并与BEM计算结果进行对比。同时,对比分析直叶片和预弯叶片风力机的功率特性、沿展向出力分布、沿展向不同截面翼型的流动特性。研究结果表明,直叶片各截面翼型的压力差较预弯叶片的大,做功能力较强。预弯通过对叶片的三维流动产生扰动,进而影响风力机的输出功率,且主要体现在叶片展向70%~90%的位置。研究成果可为风力机叶片气动性能的设计与优化提供参考。     

风力机叶片气动设计及偏载计算

风力发电机组叶片的气动特性直接影响到机组效率,考虑了风力机叶片气动损失,运用Schmitz方法对1MW定桨风力发电机组的叶片进行了气动设计.叶片从叶根到叶尖采用了不同翼型,以满足叶片强度和气动性能的要求.不同翼型之间采用了3次样条插值后的过渡翼型,同时叶根和叶尖也进行了处理,以满足工艺和实际的要求.在所设计的风力机叶片的基础上,计算了风力机的偏载特性,由于风力机起动与空载时,Schmitz方法误差较大,该文采用了Schmitz理论的扩展算法来计算风力机的偏载特性.设计结果表明,基于Schmitz理论设计的多翼型风力机叶片考虑了叶片的损失,方法简单,计算出来的叶片弦长和扭角符合实际叶片的规律.采用了扩展算法后的偏载特性曲线,考虑了各种损失,与实际风力机表现的特性规律相符.     

并网型垂直轴风力机的基本构成与气动特性

本文通过对升力型垂直轴风力机叶轮内部气流的适当简化,建立了矢量气动数学模型,分析了叶素在任意方位角下的叶片静态气动力特性,并给出了垂直轴风力发电机组运行所需要的气动条件。文章还简要讨论了垂直轴风力机的叶片设计问题,指出实度对其效率影响较大,给出实验得出的最佳实度。     

扰动入流对风力机叶片流场及输出功率的影响分析

基于漩涡法与实验条件修正入流条件,结合延迟分离涡湍流模型,对水平轴风力机气动特性进行数值模拟。分析风力机压力系数、截面涡量和功率特性,并与均匀入流和实验数据对比。研究表明,修正的扰动入流对风力机叶片叶根处截面压力系数的影响比均匀入流更大,但随翼展方向趋于一致;扰动致使在叶片0.57~0.71 R处产生更大的涡量损失,小于额定尖速比时输出功率更接近实验值。基于漩涡法的风力机气动特性模拟方案,可更有效地应用于风力发电预测研究。     

风力机叶片阻尼抑颤特性分析

基于"典型剖面"建立风力机叶片二维翼型的颤振方程,根据定常气动理论推导出气动阻尼和气动刚度。为提高叶片的抗振能力,提出向叶片添加阻尼材料来增加叶片结构阻尼的方案,并建立该方案的力学模型。对某国产600 k W风力机叶片的气动特性及阻尼抑颤特性进行数值仿真实验。仿真结果显示,阻尼结构叶片较普通叶片x向颤振最大位移、最大速度分别降低28.2%、34.8%;θ向最大速度降低了17.0%。研究结果可为风力机叶片设计提供参考。     

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。     

Fluid structure interaction of a morphed wind turbine blade

One serious challenge of energy systems design, wind turbines in particular, is the need to match the system operation to the variable load. This is so because system efficiency drops at off‐design load. One strategy to address this challenge for wind turbine blades and obtain a more consistent efficiency over a wide load range, is varying the blade geometry. Predictable morphing of wind turbine blade in reaction to wind load conditions has been introduced recently. The concept, derived from fish locomotion, also has similarities to spoilers and ailerons, known to reduce flow separation and improve performance using passive changes in blade geometry. In this work, we employ a fully coupled technique on CFD and FEM models to introduce continuous morphing to desired and predetermined blade design geometry, the NACA 4412 profile, which is commonly used in wind turbine applications. Then, we assess the aerodynamic behavior of a morphing wind turbine airfoil using a two‐dimensional computation. The work is focused on assessing aerodynamic forces based on trailing edge deflection, wind speed, and material elasticity, that is, Young's modulus. The computational results suggest that the morphing blade has superior part‐load efficiency over the rigid NACA blade. Copyright © 2013 John Wiley & Sons, Ltd.     

TMT40.3大型风力机叶片气动性能分析

基于BLADED软件平台,对TMT40.3大型风力机叶片的气动性能进行了分析.分析结果表明:TMT40.3大型风力机叶片应用在GL3A风场时的额定功率能达到1 650 kW,所承受的疲劳强度和极限载荷均能满足该款风力机叶片的设计要求,在叶尖速比为7.8～11.4的风能利用系数均在0.46以上,最高可达0.486,具有较好的气动性能和较宽的风速适应范围.     

浅析水平轴风力机叶片设计叶尖速比的选择

设计叶尖速比是风力机叶片设计中需要考虑的重要因素,文中分析了叶尖速比对叶片的弦长、载荷、气动性能、整机的功率和发电量等的影响,讨论了设计叶尖速比的选择。并分析得出增大设计叶尖速比,能够减小叶片弦长、载荷、成本,提高气动性能,但会使机组发电量有所下降的结论。     

某1 MW水平轴风力机叶片气动设计及载荷计算

基于片条理论,考虑了叶尖损失、叶根损失、叶柵影响和重载荷下对片条理论参数修正的情况下,完成了某1 MW水平轴风力机叶片的气动设计,并对其气动性能进行了评估;最后根据IEC规范对叶片在不同风况状态下进行载荷计算,所得结果可为同类风力机气动设计和结构设计提供参考。     

风雨作用下风力机流场及气动性能分析

风雨作用下雨滴会改变风力机流场及叶片气动力,影响风力机的安全和稳定运行.以某1.5 MW风力机为研究对象,基于多参考坐标系法和欧拉两相流法,得到风雨作用下风力机流场和雨滴收集率分布;在此基础上,结合欧拉壁面液膜模型对雨滴在叶片表面的累积过程进行计算,分析叶片气动性能.计算表明:风雨作用下叶片表面雨滴收集率沿展向逐渐增大...     

Load alleviation of wind turbines by yaw misalignment

Vertical wind shear is one of the dominating causes of load variations on the blades of a horizontal axis wind turbine. To alleviate the varying loads, wind turbine control systems have been augmented with sensors and actuators for individual pitch control. However, the loads caused by a vertical wind shear can also be affected through yaw misalignment. Recent studies of yaw control have been focused on improving the yaw alignment to increase the power capture at below rated wind speeds. In this study, the potential of alleviating blade load variations induced by the wind shear through yaw misalignment is assessed. The study is performed through simulations of a reference turbine. The study shows that optimal yaw misalignment angles for minimizing the blade load variations can be identified for both deterministic and turbulent inflows. It is shown that the optimal yaw misalignment angles can be applied without power loss for wind speeds above rated wind speed. In deterministic inflow, it is shown that the range of the steady‐state blade load variations can be reduced by up to 70%. For turbulent inflows, it is shown that the potential blade fatigue load reductions depend on the turbulence level. In inflows with high levels of turbulence, the observed blade fatigue load reductions are small, whereas the blade fatigue loads are reduced by 20% at low turbulence levels. For both deterministic and turbulent inflows, it is seen that the blade load reductions are penalized by increased load variations on the non‐rotating turbine parts. Copyright © 2013 John Wiley & Sons, Ltd.     

A framework for isogeometric‐analysis‐based optimization of wind turbine blade structures

Early‐stage wind turbine blade design usually relies heavily on low‐fidelity structural models; high‐fidelity, finite‐element‐based structural analyses are reserved for later design stages because of their complex workflows and high computational expense. Yet, high‐fidelity structural analyses often provide design‐governing feedback such as buckling load factors. Mitigation of the issues of workflow complexity and computational expense would allow designers to utilize high‐fidelity feedback earlier, more easily, and more often in the design process. Thus, a blade analysis framework that employs isogeometric analysis (IGA), a simulation method that overcomes many of the aforementioned drawbacks associated with traditional finite element analysis (FEA), is presented. IGA directly utilizes the mathematical models generated by computer‐aided design (CAD) software, requiring less user interaction and no conversion of parametric geometries to finite element meshes. Furthermore, IGA tends to have superior per‐degree‐of‐freedom accuracy compared with traditional FEA. Issues unique to IGA in the context of wind turbine blade design, such as coupling of thin‐shell components, are addressed, and a design approach that combines reduced‐order aeroelastic analysis with IGA is outlined. Aeroelastic analysis is used to efficiently provide dynamic kinematic data for a wide range of wind load cases, while IGA is used to perform buckling analysis. The value of incorporating high‐fidelity analysis feedback into blade design is demonstrated through optimization of the NREL/SNL 5 MW wind turbine blade. A variety of potential designs are produced with reduced blade mass and material cost, and IGA‐based buckling analysis is shown to provide design‐governing constraint information.     

气动力和离心力对风力机叶片应力影响研究

针对自行研制的NACA4415翼型水平轴风力机,通过流固耦合的数值模拟计算方法,考虑气动力和离心力以及两者耦合作用,选取叶片最大弦长、中部弦长、气动中心线展向以及最大应力点位置,分析风力机叶片在不同工况下的应力特性分布规律。结果表明:在气动力作用下,叶片相同弦长位置处迎风面应力小于背风面应力,且随尖速比和入流风速增大而增大,最大应力点位置随着尖速比增大沿翼展向外且靠近叶片前缘方向延伸;在离心力作用下,叶片相同弦长位置处迎风面应力大于背风面应力,且随尖速比增大而增大,而最大应力点均在叶根最大弦长位置(9.93 mm,10.80 mm,-126.33 mm);在耦合作用下,叶片相同弦长位置处迎风面应力大于背风面应力,随尖速比和入流风速增大而增大,且依次大于气动力和离心力产生的应力,而最大应力点均在叶根最大弦长位置。仿真结果对于风力机翼型的选择及优化设计具有重要的理论意义及参考价值。     

Aeroelastic multidisciplinary design optimization of a swept wind turbine blade

Mitigating loads on a wind turbine rotor can reduce the cost of energy. Sweeping blades produces a structural coupling between flapwise bending and torsion, which can be used for load alleviation purposes. A multidisciplinary design optimization (MDO) problem is formulated including the blade sweep as a design variable. A multifidelity approach is used to confront the crucial effects of structural coupling on the estimation of the loads. During the MDO, ultimate and damage equivalent loads are estimated using steady‐state and frequency‐domain–based models, respectively. The final designs are verified against time‐domain full design load basis aeroelastic simulations to ensure that they comply with the constraints. A 10‐MW wind turbine blade is optimized by minimizing a cost function that includes mass and blade root flapwise fatigue loading. The design space is subjected to constraints that represent all the necessary requirements for standard design of wind turbines. Simultaneous aerodynamic and structural optimization is performed with and without sweep as a design variable. When sweep is included in the MDO process, further minimization of the cost function can be obtained. To show this achievement, a set of optimized straight blade designs is compared to a set of optimized swept blade designs. Relative to the respective optimized straight designs, the blade mass of the swept blades is reduced of an extra 2% to 3% and the blade root flapwise fatigue damage equivalent load by a further 8%.