【作者】 王建宏；

【导师】 秦大同；

【作者基本信息】 重庆大学 ， 机械设计及理论， 2009， 博士

【摘要】 现代风力发电机的动力学特性是由其组成结构和工作环境的工况特点所决定的,其设计和传统机械系统的设计有着很大的区别:首先风力发电机通常工作在一些特殊工况如变风载工况甚至失速状态,其次风力发电机叶片和塔架的柔性变形对其动力学特性产生的影响不容忽视,在这些条件下还要求风力发电机主要部件的运行寿命达到20年,这对风力发电机的设计带来严重的挑战。针对风力发电机的结构特点和工况特点,本文应用多体动力学理论对风力发电机的动力学特性进行了研究,目的是为其机械系统的合理设计奠定理论基础,具体工作内容有:(1)风力发电机叶片的动力学特性。应用薄壁板理论和有限元理论建立了风力发电机叶片的数学模型,应用此模型研究了叶片的自然频率和模态,分析了叶片上的应力分布情况,初步探讨了叶片在阵风环境下的动力学响应问题。该模型既具有一维梁单元简单的优点,又能如同板、壳单元一样提供足够丰富的叶片变形和应力的信息。(2)风力发电机传动系统的动力学特性。首先根据多体动力学理论建立了在空间做任意运动的一个物体的运动方程和动力方程,然后根据传动系统中齿轮、滚动轴承以及轴系的特点通过施加约束条件进行了传动系统的多体动力学建模,从而形成传动系统的动力学方程。应用该动力学方程分析了风力发电机传动系统的自然频率和模态,研究了滚动轴承对系统自然频率的影响,给出了行星轮和太阳轮的运动和变形以及齿轮系统的动态传动误差(DTE)随啮合频率的变化规律。(3)风力发电机整机的动力学特性。通过耦合风力发电机风轮叶片模型,传动系统动力学模型以及电机模型,得到风力发电机整机的动力学模型。应用该模型研究了风轮叶片的模态,模拟了风力发电机的启动过程,给出了风力发电机在恒定风速条件下风轮叶片的变形以及行星轮和太阳轮的振动位移,分析了传动系统中行星齿轮与内齿轮和太阳轮的动态啮合力。(4)风力发电机柔性部件的变形和应力。作为风力发电机中最主要的两个柔性部件,叶片和塔架的柔性变形对风力发电机的性能有着重要的影响。由于这两个部件都是薄壁构件,通过定义薄壁构件的变形方程,得到叶片和塔架以及机舱的动能和势能,依据拉格朗日方程建立了系统的动力学方程,分析了叶片和塔架的自然频率和模态,计算了叶片和塔架的应力和位移分布并给出了塔架的刚度对叶片翼尖位移的影响。(5)风力发电机传动系统滚动轴承和齿轮系统的耦合研究。根据滚动轴承的几何特点和Hertz接触理论,建立了滚动轴承的非线性位移和受力关系表达式。将滚动轴承和行星齿轮的变形通过轴系加以耦合,从而导出表征滚动轴承和行星齿轮耦合关系的非线性系统方程。应用该模型研究了系统的振动模态并对行星齿轮的变形和接触力进行了分析,计算了滚动轴承的变形。本文对风力发电机的机械动力学特性特别是传动系统的动力学特性进行了深入研究。建立了风力发电机整机柔性多体动力学模型,特别是传动系统中齿轮、滚动轴承以及轴系的精细动力学模型,依据该模型分析了风力发电机的动力学特性,模拟了风力发电机各部件的动力学响应。为风力发电机机械系统的科学设计提供了理论支持。更多还原

【Abstract】 The dynamic of a modern wind turbine is governed by the complex interaction of its subsystem and its design requires the skills of a multidisciplinary knowledge with expertise in diverse area: atmospheric wind flow, rotor aerodynamics, control, mechanical systems, electrical systems and civil engineering. The design problem is particularly complicated since wind turbines have little respect for engineering conventions: first, the wind turbine is required to operate in stall; second, it is subject to highly irregular inputs and finally it is required to work over 20 years with unattended operation. Based on the listed wind turbine’s unique natural, the followed areas are put special interest:(1) The dynamical behavior of blade. The mathematical modeling of the wind turbine’s blade is established based on the theory of thin-wall beam and finite element theory, and it is applied to investigate the natural frequencies and corresponding mode shape, analyze the stress distribution on the skin of the blade and rudimentarily research the dynamical response under condition of gust. This modeling not only inherits the simplicity of the beam element, but provides rich information on the displacement and stress as well.(2) The dynamic of drivetrain of wind turbine. Firstly, the kinematic of an object with arbitrary spatial movement is defined based on theory of multibody, and then the constraints are exerted on condition of characters of each component movement within the drivetrain and thus formed the system’s governing equation. Finally the natural frequencies and mode shape are described; the influence of bearing stiffness on the natural frequency are shown; the floating of planet and sun are pictured and the dynamical transmission error varying with the frequencies are given.(3) The dynamic of the wind turbine. Through coupling the mathematical modeling of rotor, drivetrain as well as generator, the modeling of wind turbine is obtained. Applying this modeling, we investigated the mode shape of the rotor, simulated the start process of the wind turbine, research the floating of planet and sun under the condition of constant wind speed and finally analyzed the dynamical contact force between planet and sun and planet and ring respectively.(4) The deformation and stress distribution of flexible component at wind turbine. As the most flexible components at the wind turbine, tower and blade play a critical role in the dynamical behavior of wind turbine. Due to the fact that both of them are thin-walled structures, the kinetic energy and potential energy of tower, blade and nacelle are obtained by defining the consistence deformation expressions for them. The system governing equation is gained by applying Lagrange function. Using them as foundation to analyze the natural frequency and mode shape of tower and blade, calculate the distribution of the displacement and deformation of tower and blade and compare the influence of various tower stiffnesses on the blade’s tip dynamical response.(5) The coupling of bearings and gear chain at drivetrain of wind turbine. At many previous research works, the stiffness of the bearing was simplified as linear infinite spring, and obviously the structure characters of bearing make this simplification have limitation. In this paper the bearing’s nonlinear relationship between force and deformation is established according the bearing’s geometry and Hertz contact theory, then the system equation is induced which govern the coupling behavior of bearing and gear chain.This thesis is focus on the mechanical dynamic behavior of wind turbine, the establishment of the component’s mathematical modeling, simulation of the wind turbine’s operation and the analysis of the mechanical characters of wind turbine更多还原