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Fluid-structure interaction analysis of a large wind turbine under yaw condition
PAN Maohua, SHENG Qihu, ZHANG Xuewei
Deep-sea Engineering Technology Research Center, Harbin Engineering University, Harbin 150001, China
Abstract: The analysis on the blade deformation and vibration of a large wind turbine is of great significance to the safety of a large blade. In the paper, a mathematical model for the bidirectional fluid-structure interaction(FSI) of a large wind turbine was established on the basis of blade element momentum theory(BEMT) and finite element theory of Euler-Bernoulli beam, the non-constant BEMT containing yaw amendment and tip hub was used to calculate the aerodynamic load of wind turbine; 2-node 12-DOF Euler beam element was used for the dynamic analysis of structure, and a new method was established by combining the two theories to quickly analyze the output characteristics and vibration characteristics of the blade of a wind turbine under the action of FSI. Through analyzing the calculation of NREL 5 MW large wind turbine, the feasibility of the method was verified and the output characteristic curve of wind turbine and the deformation of blade structure were obtained under the condition of fluid structure interaction. It proves that vibration occurs when the wind turbine lies in operatingstates. In addition, under yaw condition, the power output and thrust output of a turbine will lead to periodic fluctuation.
Key words: wind turbine     yaw condition     fluid-structure interaction     blade element momentum theory

1 气动力模型

BEM理论对于具有可靠二维翼型气动特性数据的三维叶片，可以方便快速地预测出风力机的气动性能。本文采用非定常叶素动量理论[2]并通过偏航模型、叶尖轮毂修正模型、动态尾涡模型、Du-Selig模型[12]进行了修正。在此只对Du-Selig模型进行详细表述，其他模型可以参见文献[1-2, 13]

Du-Selig失速模型假设三维翼型数据可以通过对二维翼型数据中的升力系数增量相加和阻力系数中的减量相减得到。如果将ΔCl作为升力系数的增量而ΔCd作为阻力系数的减小量，则三维修正表达式可以表示如下：

2 结构动力模型

 图 1 单元模型
3 耦合过程

 图 2 双向耦合示意图
4 数值计算及分析

4.1 无偏航情况

 图 3 单向耦合与无耦合功率对比

 图 4 单双向耦合条件下功率输出对比

 图 5 风速15 m/s下单、双向耦合振型对比
4.2 有偏航情况

 图 6 偏航条件下的推力和功率输出对比
 图 7 偏航条件下的叶尖振动

5 结论

1) 无偏航时，叶片的振动与变形导致风轮功率输出的波动；

2) 叶片运行过程当中发生振动，挥舞方向的叶尖振幅大于拍振方向；

3) 有偏航时，风轮输出特性及叶尖振动呈周期性变化；

4) 控制叶片的振动有利于输出稳定。

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文章信息

PAN Maohua, SHENG Qihu, ZHANG Xuewei

Fluid-structure interaction analysis of a large wind turbine under yaw condition

Applied Science and Technology, 2017, 44(1): 1-4
DOI: 10.11991/yykj.201605008