基于湿-热-弹本构和刚柔耦合理论的变桨旋转风力机叶片动力学特性研究

There are many special hygrothermal characteristics in wind farms of China; for instance, the temperature difference is usually large in wind farms of the north area, and the humidity is often high in those of the south area and offshore wind fields. The change of temperature and moisture absorption will alter the mechanical properties of composite material of blades, which will induce the shift of parameters of blades. Furthermore, the dynamic characteristics of the blades will vary with the change of blade parameters. In extreme cases, this influence can lead to the instability of wind turbines and cause accidents. There have been lots of researches on dynamic characteristics of rotating wind turbine blades with pitch motion, which have taken into the consideration of the influence of temperature and humidity. However, few of them cared about the hydrothermal influence on mechanical properties of composite, and also few of them considered rigid-flexible coupling between blade deformation and pitch motion. This project plans to investigate the dynamic characteristics of wind turbine blades with pitch motion from these two special perspectives. By introducing the hydrothermal effects through hygrothermoelastic constitutive theory, and based on rigid-flexible coupling theory, the nonlinear dynamical model of the inherent rigid-flexible coupled system will be established to describe the dynamic problem of pitching blade subjected to hydrothermal influence, while coefficients of the governing equations depend on temperature and humidity. Analytical methods of linear and nonlinear vibration of the inherent rigid-flexible coupled system with hydrothermal-variable parameters will be further studied, and then the vibration characteristics and stability of blades will be discussed. It is expected to achieve innovative theoretical results in dynamic modeling, dynamic characteristics analysis, and stability analysis of the inherent rigid-flexible coupled system with temperature-humidity-induced variable parameters through the study of this project. The coupling influence between blade deformation and pitch motion, the influence mechanism of temperature and humidity, and the influence of important design parameters on dynamic characteristics of blade will be revealed, which will provide theoretical reference for the pitch control and operation stability control of wind turbine blades working in complex environment.

我国风场通常具有温度跨度大、湿度高的特征。温度变化和吸湿将改变复合材料的力学性质，使叶片参数发生变化，进而改变叶片动力学特性，极端情况下可导致风力机运动失稳，引发事故。但是，目前考察温湿影响的变桨旋转风力机叶片动力学特性的理论研究，较少从温湿对材料性质影响的角度分析问题，亦较少涉及叶片变形与变桨运动的刚柔耦合效应。本项目拟考察变形-变桨刚柔耦合效应，并通过湿-热-弹本构引入温湿对材料的力学性质的影响，建立温湿诱导的变参数自身刚柔耦合系统非线性动力学模型，描述温湿影响下变桨旋转叶片动力问题，进一步研究温湿变参数刚柔耦合系统线性振动和非线性振动的分析方法，藉此探讨叶片动力学特性。项目预期在温湿诱导的变参数自身刚柔耦合系统的动力学建模、动力特性分析和稳定性分析方面取得创新性理论成果；揭示变形-变桨耦合影响、温湿影响、重要设计参数的影响，为复杂环境下叶片变桨控制和运行稳定性控制提供理论依据。

降低弃风率和增强环境适应性是我国风电机组研发所面临的两个重要问题。研究复杂环境下变桨旋转风力机叶片动力学特性、气动性能和变桨控制策略，可为降低弃风率、增强风力机环境适应性提供参考依据，具有重要的工程价值。同时，相关研究可为非线性动力学、风力机气动性能等领域提供新的模型和方法，具有重要的科学意义。本项目的研究内容和重要结果如下：(1) 将叶片主梁简化为复合材料薄壁梁，通过湿-热-弹本构引入温度和湿度对材料性质的影响， 考虑轴向变形-面内弯曲-面内剪切-面外弯曲-面外剪切-扭转-翘曲耦合效应、非线性、铺层方式、旋转、外力、截面非均匀性、约束扭转、安装角、预扭角等因素，采用哈密顿原理建立了薄壁梁温湿变系数动力学模型。研究了模型的简化问题，给出了多种形式的简化模型。(2) 探讨了使用温湿变系数动力学模型处理静力学和动力学问题的方法。分析了静态扭转、湿热内力等静力学问题，研究了弯弯耦合振动、拉扭耦合振动等动力学问题，揭示了温度、吸水浓度、安装角、铺层角、转速、模态耦合等因素对静态变形、湿热内力、频率、模态、内/外共振频率等静/动力学特性的影响。(3) 研究了高尖速比垂直轴风力机叶片、低风速时水平轴风力机叶片的气动性能和变桨优化问题，提出了变桨控制规律，揭示了风速、转速、入流速度比、叶尖速度比、方位角、旋转半径、弦长等因素对转矩、转矩系数、功率、功率系数和最优桨矩角的影响。(4) 考虑变桨-变形耦合效应，得到自身刚柔耦合动力学模型，分析了变桨运动对线性/非线性振动特性的影响，揭示了一类参数敏感性系统。(5) 研究了叶片结冰工况下的大水滴撞击翼型的破碎过程，以及动态失速时叶片的气动性能。本项目研究为复杂环境下叶片变桨控制和运行稳定性控制提供了理论参考依据，为动力学研究提供了一套温湿变系数自身刚柔耦合非线性动力学模型和处理方法，为叶片变桨优化控制提供了一套处理方法和变桨控制策略。