近海风力机失速诱导的气弹失稳问题研究

Modern large scale wind turbine blades and some other compnents are provided with the characteristic of high flexibility and turbines are usually installed in offshore environment. The stall-induced aeroelastic instability is a important factor that affecting the turbines stable operation. The risk of stall indueced vibrations and areoelastic stability of the offshore wind turbines is studied in this project applying the theory of nonlinear elasticity, dynamic aerodynamic theory and nonlinear wave theory. By means of theoretical analysis, wind tunnel experiments and other research techinques, it is intended to research for the feedback effects of the flexible deformation of the components to the flow field，especially the dynamic stall aerodynamic problems, to research for the coupled vibration of the rotor, drive chain and tower, and the variation of the directons of blade vibrations relative to the rotor plane and the changing mechanism of the dynamic aerodynamic damping, to research for the nonlinear characteristics of waves in shallow water and the interference effects between the large-size tower and the waves, and then to explore the coupling mechanisms associated with the hydrodynamic, dynamic aerodynamic and the vibration of the turbine system. The system nonlinear dynamic equations that can accurately reflect interaction between the aerodynamic, wave loads and the struture flexibility are constructed by application of multi-body sysytem dynamics models. The sysytem aeroelastic stability characteristic equation is derived from linearization of the dynamic equations and determination the stall-induced aeroelastic instability boundary and relative system parameters.This investigation will provide theory and analysis method support for the autonomous design and scurity, stability operation of the new large-scale flexible offshore wind turbines.

现代大型风力机具有叶片等构件高柔性的特点且通常安装在近海，失速诱导的气弹失稳是影响风力机稳定运行的重要因素。本项目拟应用非线性弹性理论、动态气动理论和非线性波浪理论，对近海风电机组失速致振及气弹稳定性进行研究。通过理论分析、风洞实验等手段，研究构件柔性变形对流场的反馈作用、尤其是动态失速时的相关空气动力学问题；研究风轮、驱动链和塔架的耦合振动，叶片相对于风轮平面的振动方向的变化规律及动态气动阻尼的变化机理；研究浅水域海波的非线性特性及其与大尺寸塔架间的干涉效应，进而探讨水动力、动态气动力与系统振动间的耦合机制。应用多体系统模型建立可正确反映气流、波浪与结构柔性相互作用的系统非线性动力学方程，再通过动力学方程的线性化，导出系统气弹稳定性特征方程，从而确定失速诱导的气弹失稳边界及相关系统参数。为新一代大型、柔性近海风电机组的自主设计与安全稳定运行提供理论和分析方法的支撑。

本项目应用非线性弹性理论、动态气动理论和非线性波浪理论，对近海风电机组失速致振及气-液-弹性耦合特性进行研究。采用“超级单元”模型，将叶片、塔架和主轴离散为通过转动铰和弹簧、阻尼器连接的刚体系统，以反映这类构件较大的弹性变形和非线性振动。在叶素动量理论(BEM)基础上，引入B - L 动态失速模型，以反映气动载荷的动态特性。考虑到气弹耦合，将叶片截面的振动速度和扭转挠曲引入到入流角和功角的计算表达式中。基于多体系统(MBS)动力学理论和气动模型，通过仿真程序自动建立受约束的风力机气弹耦合方程。数值模拟了机组的时域气弹响应。通过施加不同的约束条件，定量分析了叶片弯曲振动和扭转挠曲对其气动载荷的反馈作用，研究了风轮以外其他构件振动对叶根气弹载荷的影响；通过静、动态气动分析模型，考察了叶根和塔底气弹载荷的动态耦合效应。分析表明，塔架、主轴等构件的运动会显著影响叶根的气弹载荷；叶片的动态失速特性对叶根的气弹载荷和疲劳载荷谱有较明显的影响。研究工作对于保证风力机安全稳定运行和疲劳寿命设计有重要的作用。.考虑构件弹性变形及风轮旋转，用刚性积分方法对系统非线性控制方程进行数值求解，通过谱分析实现了系统运转模态识别，研究了系统前若干阶模态变化及影响因素。结合柔性叶片振动模态参数包括模态频率、模态向量和模态质量等物理量的识别和振动能量损失法，即计算气动力在叶片振动周期内所做的功，导出了叶片模态气动阻尼比计算式。研究结果可作为风力机系统气弹稳定性判据。.分别应用线性波理论和非线性波浪（二阶波）模拟非规则的波浪；应用Ｍorison公式建立作用于塔架支撑基础的波浪力计算模型。结合气动载荷模型、波浪载荷模型和高效的数值求解方法，建立了海上风力机系统的动力学模型，实现了流固耦合动力响应数值分析。研究工作为新一代大型、柔性近海风电机组的自主设计与安全稳定运行提供了理论和分析方法的支撑。