基于主动式双变桨叶片的10MW级大型风力机叶片颤振控制研究

Classical flutter is one of the most destructive aeroelastic instability phenomena of large-scale wind turbines. In 2003, twenty five wind turbines were hit by the typhoon "Cuckoo" in Shanwei Red Bay commercial wind farm (an offshore hilly land), nine of them were damaged due to the classical flutter. This cased a huge loss of local wind power system. The traditional blades, which implemented with full-span pitch angle to optimize the aerodynamic loads and energy production, may encounter stall flutter instability. Moreover, pitch-bearing fatigue and the usage of the pitch actuators limit the application of such blades. The next generation wind turbines in China with rated power of more than 10-megawatt will implemented with longer, softer and slender blades. Hence, they are more inclined to flutter instability than currently utilized wind turbines. The classical flutter of wind turbine blade is caused by the action of aerodynamic load, elastic load and inertial load, and is relevant to some primary parameters such as the rotational speed of the rotor and the ration between bending and torsional mode of blade. However, rarely studies have been performed to address this flutter problem. Until now there is no applicable solutions for this issue. Hence, the present project is intend to develop an actively double-pitched blade (i.e. both inner and tip part of blade are separately pitched) to suppress flutter of large-scale wind turbine blades through the combination of numerical simulations and wind tunnel experiments. Firstly, the mechanism of the active control system are investigated, the mathematical relationship between the blade tip control force and the reference pitch angle of blade tip will be formulated based on the forced vibration experiments. Secondly, aerodynamic coefficients of blade will be estimated through both static and dynamic wind tunnel experiments, and the 3D effect due to the down wash at blade tip on the aerodynamic loads of blade will also be investigated. Finally, the double pitched aero-servo-elastic wind turbine model will be established based on the experiment results, numerical simulations will be conducted to obtain the optimal parameters relevant to the flutter suppressing design. The present subject aiming at increasing flutter-suppressing performance of the 10+megawatt wind turbines of our country, is closely related to the construction and development of China wind power industry, and has significant theoretical and practical importance.

叶片颤振失稳是大型风机最具破坏性的气弹现象。2003年汕尾市红海湾风电场9台风机叶片发生大幅扭转颤振破坏，造成巨大经济损失和社会影响。传统风机叶片采用单一变桨控制系统优化桨距角和发电功率，但存在无法迅速反应变桨以及叶片大攻角颤振失稳的风险，同时根部变桨控制器的耐久性和经济性也制约了其大型化趋势。我国下一代10MW风机颤振临界转速理论值接近额定转速，因此开发经济有效的抑颤措施是推动风电技术进一步发展的关键问题之一。鉴于此，本项目拟开发一种叶片尖部、基部独立变桨的新型主动式双变桨叶片，提出全耦合双变桨叶片风机模型抑颤分析方法，研究叶尖主动控制策略提升抑颤性能。主要内容包括：1)大攻角范围内风力机叶片的气动力特性；2)全耦合双变桨叶片风机模型建模及时域气弹稳定性分析方法；3)叶尖主动控制策略及时滞的鲁棒性分析，控制参数优化研究。课题紧扣我国风能产业趋势，将进一步推动风电技术发展。

1.研究背景.风力机尺寸的大型化、叶片细长化成为必然的发展趋势。然而随着风力机尺寸的不断增大，叶片结构也变得越来越细柔，叶片颤振问题变得越发突出。..2.研究内容.本项目拟提出一种新型主动式双变桨叶片设计，实现对10MW风力机柔性叶片颤振失稳的主动控制。项目研究内容主要包括四项：1)双变桨叶片叶片尖部控制力与目标桨距角关系研究;2)叶尖三维效应以及叶片气动力系数测定;3)风力机全耦合气弹动力学模型建模以及颤振特性研究;4)双变桨叶片风力机气弹动力学模型建模以及颤振控制参数优化...3.重要结果、关键数据.（a）风机气弹响应研究发现：叶片挥舞方向频率成分主要包括一阶塔架弯曲模态和挥舞。摆振方向频率成分主要包括一阶塔架弯曲模态和摆振。对于风力机塔架而言，主要频率成分为塔架一阶弯曲模态频率，而塔架的动态响应受叶片影较小。气动阻尼对叶片挥舞方向以及塔架顺风影响最大。而叶片摆振方向、扭转以及塔架横风气动阻尼值较小。.（b）主动式双变桨叶片抑颤研究发现为：叶片尖部长度以及转轴位置为影响颤振关键结构参数。叶片尖部最优长度为叶片长度的3.3%，叶片尖部转轴最优位置约在弦长中点。在尖部长度和尖部转轴位置最优时，该双变桨叶片叶尖扭转幅值仅为原颤振临界状态下扭转幅值的3.8%左右。此外叶片尖部各个截面挥舞方向弯曲刚度最大值在30%弦长左右，且摆振方向刚度较大，最大值在叶片后缘处，最小值在30%弦长左右；扭转刚度最小值在20%弦长附近。..4.科学意义及应用前景.本研究课题针对大型叶片极易发生的颤振失稳问题，首次提出了新型双变桨叶片设计。该新型叶片能根据实时气动力荷载迅速变桨调整，解决了传统整个叶片变桨的缺陷，同时解决了叶片维护成本高的缺点。是今后商用大型风力发电机叶片设计的有效备选方案之一。 本课题紧扣风能技术研究的学科前沿，符合我国《能源技术革命创新行动计划（2016-2030年）》战略研究方向。因此，本课题研究成果具有较好的应用前景。