大型化趋势下风力机叶片刚度降低,出现颤振的风险增加,且风力机在运行中不可避免受到非均匀来流的影响。为考虑这一问题,对垂直方向波动来流中具有结构非线性的翼型气弹稳定性进行研究。基于小攻角假设,采用线性气动力模型建立考虑三次硬化刚度与非均匀来流作用下的二自由度二维翼型气弹模型,并通过数值积分方法对翼型气弹系统的动力学方程进行求解,得到不同来流工况下翼型系统的稳态响应形式。从时域、相轨迹以及频域上对获得的翼型振动信号特征进行分析,结果表明翼型受到垂直方向来流的激振作用出现强迫振动,在低流速下和临界速度附近造成振动强度明显放大,模糊颤振边界并使诱发颤振条件下翼型振动更加剧烈;在波动来流作用下气弹失稳的俯仰振动能量在一个频率带上分布,且在高于颤振频率的位置存在另一峰值,标志颤振的诱发是由俯仰振动受到气动力影响耦合到沉浮频率上所导致。
Abstract
The trend of large-scaling in wind turbines decreases the blade stiffness and lifts the risk of blade flutter. Meanwhile, the blade is also inevitably affected by the non-uniform inflow during real-world operations. To inquire into this problem, the aeroelastic stability of airfoil with structural nonlinearities placed in vertically fluctuating non-uniform inflow is investigated. Based on the assumption of small angle of attack, taking the cubic-stiffening suspension and non-uniform inflow into account,a two-dimensional,two-degrees-of-freedom aeroelastic model is established by using the linear aerodynamic modle. The dynamic equation of the aeroelastic systern for airfoil is then solved via numerical integration method, and the steady-state response forms of air foil system under different inflow conditions are obtained. The characteristics of the oscillation signal are analyzed from the time-, phase- and frequency- domains. The results show that the airfoil undergoes forced oscillation caused by the excitation of the vertical inflow. The non-uniform inflow also amplifies the flutter at low and near-critical airspeeds, obscures the boundary of the flutter onset, and makes the induced flutter conditions of the airfoil more severe. It is also found that the pitch oscillations have a frequency distribution which peaks at higher than the flutter frequency,indicating that the flutter onset is caused by the frequency shift from the pitch to the plunge oscillations.
关键词
风力机 /
气动弹性 /
颤振 /
数值分析 /
结构非线性 /
非均匀来流
Key words
wind turbines /
aeroelasticity /
flutter /
numerical analysis /
structural nonlinearity /
non-uniform inflow
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基金
国家重点研发计划（2020YFB1506601）; 上海市科技创新行动计划（20dz1205300）
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