针对超长柔性风电叶片在传统线性（小变形）条件下发生动力学分析失效的问题,提出考虑大变形结构的柔性叶片模型并进行气动弹性分析。首先将叶片简化成非均匀悬臂梁,利用大变形Euler-Bernoulli梁模型进行离散化建模;后结合叶素动量理论,建立叶片的非线性结构动力学方程,并运用Newton-Raphson和逐步积分相结合的方式进行时域仿真。整个过程重点考虑大变形结构的刚度变化、以及柔性叶片截面扭转运动和外形变化。以DTU 10 MW风力机为算例,比较叶片在大变形和小变形结构下的动态气动特性,结果表明：动态响应中,大变形结构的刚度变化导致挥舞方向的叶尖位移明显增加,略微减小摆振方向的位移,同时叶尖扭角也会显著减小。此外,叶根面外载荷在大变形条件下会显著下降,但叶根面内载荷则会略微增加。这与传统线性条件下的气弹现象具有明显差异。该文的叶片模型能有效预测长柔叶片的动态气动特性。
Abstract
Aiming at the problem of dynamic analysis failure of ultra-long flexible wind turbine blades under traditional linear (small deformation) conditions, a flexible blade model with the large-deflection structure is developed to study the dynamic response. The blade is simplified as a cantilever and discretely modeled by applying the large-deflection model which is derived from the Euler-Bernoulli beam. Then, the nonlinear aeroelastic dynamics equations of the blade model are established by using blade element momentum （BEM） theory, and time-domain simulations are performed by using the nonlinear Newmark method and Newton-Raphson method. The changes of the structural stiffness and the pose of the blade are considered throughout the process. Finally, the nonlinear model is applied to the DTU 10 MW wind turbine. The results show that the large-deflection model significantly increases the flapwise deflection and torsion angle of the blade tip in dynamic response, while slightly reduce the edgewise deflection. Meawhile, the large-deflection model significantly reduces the flapwise load of the blade root in dynamic response, while slightly increase the edgewise load of the blade root, which is different from the result of the linear model.
关键词
风力机 /
柔性叶片 /
大变形结构 /
气动弹性 /
截面扭转
Key words
wind turbines /
flexible blade /
large-deflection /
aeroelasticity /
cross-section twist
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