风力发电机塔筒顶部法兰的有限元分析

使用非线性有限元软件MSC.Marc/Mentat建立风力发电机塔筒顶部法兰联接的有限元模型,施加合理的边界条件和载荷后,通过非线性接触分析得到在预紧工况和极限工况下各组件的应力分布和变化情况,并对塔筒顶部法兰接触面进行安全性校核和塔筒顶部法兰与塔筒筒体焊缝处的疲劳寿命分析。分析结果表明,该塔筒顶部法兰的强度、安全性和焊缝处的疲劳寿命均满足设计要求,且结果为大型风力发电机法兰合理设计和性能强化提供了科学依据。     

Output-only modal analysis of wind turbine tower based on vibration response under emergency stop

The identification technique of output-only modal parameters is proposed for the large wind turbine tower under emergency stop. Compared with the response of regular operating conditions, the immediate tower structural response under emergency stop much more resembles a state of free vibration, which is more appropriate for the modal identification of the wind turbine tower. The vibration response is measured in the nacelle, which is easy to perform in the field modal test. The variational mode decomposition (VMD) is applied to decompose the vibration response into several band-limited intrinsic mode functions. The free responses of decomposed functions are extracted by applying the random decrement technique (RDT). Finally, the modal damping ratio and natural frequency are identified from each free modal response by using the Hilbert transform method. Simulations and a 1.5 MW wind turbine field modal test results verify the effectiveness of the proposed identification method. The main modal parameters of wind turbine, including weak modes, are effectively extracted by using output-only vibration responses under emergency stop. The modal parameter identification method is provided for the large wind turbine structure under the engineering condition.     

风力发电机组塔筒的横向振动分析

结合有限元方法和工程计算对风力发电机组塔筒的横向振动进行分析.通过塔筒固有频率和风振频率的对比,判断塔筒容易发生共振的区域.给出并分析塔筒发生横向振动时塔顶最大位移、惯性力和特征弯矩的简化计算方法,并给出算例.计算了塔筒发生横向振动时的疲劳损伤.结果表明塔筒底部容易因横向振动而发生共振.     

风电机组塔筒载荷的测试与分析

以风电机组塔筒为研究对象,对风电机组塔筒载荷特性及计算方法进行分析研究。在介绍塔筒载荷测试主要参数及方法的基础上,采用应变测试方法,对一台1.5 MW风电机组塔筒在启动、运行、正常停机等多种工况及不同平均风速下进行载荷测试,得到了塔筒根部弯矩、转矩及1阶固有频率,并与仿真计算结果进行了对比。结果表明,实测结果与仿真结果接近,仿真模型可用于机组载荷计算和动态性能分析。     

IDC机柜结构地震工况非线性时程分析研究

文中以互联网数据中心(Internet Data Center,IDC)机柜为研究对象,在Radioss软件中进行该机柜地震工况的非线性时程仿真研究.通过对有限元模型单元类型、网格尺寸和网格质量的控制,达到与物理实验的对标.文中进行了材料力学性能试验,标定了冷轧钢板的材料模型参数,同时还分析了沙漏能控制模式对计算结果的...     

下风向风力机风轮直径的最优解

针对现有风轮直径计算精度的不足,根据提出的下风向风力机风轮扫掠面积上能量分布数学模型,推导出了考虑风剪切与塔影效应在内的精确能量获取计算式。结合具体算例,对风轮直径的3种不同计算格式分别予以求解。计算结果表明:风剪切对风力机风轮直径的影响甚小,塔影效应影响明显,塔架高度影响最大;风轮直径与塔架直径近似成线性关系;塔架高度存在极值;存在满足能量输出要求的最优尺寸匹配关系。     

基于Comsol Multiphysics的海上风力机塔架模态分析

塔架是风力机的主要支撑装置,鉴于海上特殊的工作环境,塔架振动在所难免。以海上3MW风力机塔架为对象,应用有限元分析软件Comsol Multiphysics对其进行模态分析,除了考虑叶轮激励频率的影响外,还要研究波浪频率对塔架的影响,通过求解有限元特征方程,得到前六阶固有频率及振型,确定引起塔架与外部激励共振主要取决于塔架的低阶频率;摆振是风力机塔架的主要振动,造成塔架顶端振幅较大。通过进行模态分析,为塔架设计、安全运行和结构动力学分析提供更可靠的理论依据。     

基于控制方法的风机塔架减振研究

为利用控制方法减小兆瓦级风机运行过程中塔架的振动量,对塔架结构动态特性和塔架激励源动态特性进行了分析研究。以某2 MW机组为例,进行了塔架振动情况评估。基于评估结果,设计了增加气动阻尼的塔架振动控制方法,并进一步设计了直接加阻的主动控制结构,结合振动过大时主动降功率运行手段,实现了塔架振动的控制器干预。在许继WRTS-800和PRDS-600仿真实验平台上进行了仿真验证和等效疲劳载荷计算;在实验风场进行了现场实验,并对实验数据进行了统计分析。研究结果表明,采用该方法,塔架等效疲劳载荷明显减小,主动控制减振效果明显。     

兆瓦级风电机组行星轮系有限元分析

针对兆瓦级风电齿轮箱中行星轮系易出故障的特点,通过三维建模软件建立行星轮系的计算模型,利用有限元方法对行星轮系进行了静强度分析,找出了最大应力点,提出了改善最大应力的方法。对行星轮系模态分析结果与已知的实际频率比较表明：在正常工作状态下,行星轮系不会产生共振。此方法为2．0MW风电机组行星轮系的设计提供了理论依据。     

A model for yawing dynamic optimization of a wind turbine structure

A novel design optimization model for placing frequencies of a wind turbine tower/nacelle/rotor structure in free yawing motion is developed and discussed. The main aim is to avoid large amplitudes caused by the yawing-induced vibrations in the case of horizontal-axis wind turbines or rotational motion of the blades about the tower axis in case of vertical-axis wind turbines. This can be a major cause of fatigue failure and might severely damage the whole tower/nacelle/rotor structure. The mathematical formulation considers a single pole tower configuration having thin-walled circular cross section with constant taper along the tower height. The nacelle/rotor combination is modeled as a rigid mass elastically supported at the top of the tower by the torsional spring of the yawing mechanism. Adequate scaling and non-dimensionalization of the various parameters and variables are given in order to make the model valid for a variety of wind turbine configurations and types of the material of construction. The resulting governing differential equation of motion is solved analytically by transforming it into a standard form of Bessel's equation, which leads to the necessary exact solutions for the frequencies and mode shapes. Several cases of study are examined for different values of the yawing stiffness and inertia parameters by considering both conditions of locked and unlocked yawing mechanism. Useful design charts are developed for placing the frequencies at their needed target values with no penalty of increasing the total structural weight of the system. In all, the developed model guarantees full separation of the system frequencies from the critical exciting yawing frequencies by proper choice of the optimization design parameters.     

Numerical analysis and experimental investigation of modal properties for the gearbox in wind turbine

Wind turbine gearbox (WTG), which functions as an accelerator, ensures the performance and service life of wind turbine systems. This paper examines the distinctive modal properties of WTGs through finite element (FE) and experimental modal analyses. The study is performed in two parts. First, a whole system model is developed to investigate the first 10 modal frequencies and mode shapes of WTG using flexible multi-body modeling techniques. Given the complex structure and operating conditions of WTG, this study applies spring elements to the model and quantifies how the bearings and gear pair interactions affect the dynamic characteristics of WTGs. Second, the FE modal results are validated through experimental modal analyses of a 1.5 WM WTG using the frequency response function method of single point excitation and multi-point response. The natural frequencies from the FE and experimental modal analyses show favorable agreement and reveal that the characteristic frequency of the studied gearbox avoids its eigen-frequency very well.     

基于VB和ANSYS的风机塔简参数化建模与分析

为了高效、快速地建立风机塔筒的有限元模型并对其进行有限元分析,对系列机型塔简模型的结构进行了全面的研究,采用ANSYS提供的APDL语言和命令流编程的方法,开发了一种风机塔筒的有限元参数化建模、分析及后处理程序,用可视化界面语言VB对其进行了封装。以塔简模型分析为实例,跟传统方法作对比,对该程序进行了验证。研究结果表明,该程序能够提高有限元模型的建模效率,缩短了塔筒的设计周期,并且简单实用,为类似问题的解决提供了一条新途径。     

基于钻头-岩石碰撞的激振冲击系统的非线性动力学研究

为了提升旋转冲击钻井过程中轴向冲击的辅助破岩效果,设计了一套用于测试钻头与岩石之间激振碰撞的试验装置,通过对钻头的激振频率、激振振幅和施加的静态压力3项可控参数的调节,研究了该激振冲击系统的动力学行为演化规律,且试验测试结果与数值模拟结果具有很好的一致性。通过进一步的分岔分析和相平面分析发现,由于激振冲击系统具有典型的接触非线性结构,其动态响应也呈现出复杂的非线性特征,钻头在与岩石发生激振碰撞后,主要保持单周期的振动状态,但随着控制参数的变化,钻头与岩石之间在一个激励周期内的碰撞次数会不断改变;此外,钻头的振动状态还会经由倍周期分岔转变为双周期振动,但最终又会经由逆倍周期分岔或者折叠分岔重新回到单周期振动状态。由于钻头的振动状态直接决定了其轴向冲击力的大小,因而会影响其破岩效率;因此,为了获得破岩效率最高的一周期一次碰撞的钻头振动状态,应该采用较高的激振频率和振幅,但应该避免较高的静态压力,因为它将触发钻头的颤振,反而降低其破岩效率。     

风电机组传动链的动力学仿真研究

针对风电机组传动链在工作转速范围内的扭转共振问题,基于GL2010标准,结合动力学仿真软件SIMPACK和有限元分析软件ANSYS,建立了某兆瓦级风电机组传动链的多柔体动力学仿真模型,并使用模态分析方法对传动链动力学仿真模型进行了频域响应分析,基于2D坎贝尔图和模态能量分布图,筛选出了传动链的潜在共振点,最终通过时域仿真分析,对相关部件的加速度进行了傅里叶变换,进一步验证了该潜在共振点是否是实际的危险共振点。研究结果表明,该机型风电机组传动链不存在危险的共振频率,在工作转速范围内能够安全稳定地运行;该方法可为风电机组的稳定性和可靠性设计提供依据。     

非线性动力学理论与大型火电机组振动故障综合治理技术

应用非线性动力学理论的Ｃ—Ｌ方法,对当前国内外大型火电机组轴系存在的若干关键振动问题,建立了转子非线性动力学模型,从理论、实验和数值计算方面,对各种故障因素影响下的动力学行为进行了综合分析,提出了对轴系振动故障进行综合治理的方案,在天津某电厂应用后取得了巨大的经济效益和社会效益     

不同P-Y数据对于海上风电机组结构频率影响分析

海上风电机组的载荷计算工作首先需要解决整机频率计算问题,以保证整机运行在合理的安全频率范围内.针对这一问题,以Aeroflex和Bladed两款仿真软件为仿真平台对整机频率进行了仿真计算,建立了基于东海大桥海上风机为研究对象的仿真模型.在分别考虑0.8倍的p-Y数据,1.2倍的P-Y数据以及海底桩基冲刷等情况下,仿真计算了不同海洋桩基环境整机模态频率.将两款仿真软件的模拟分析结果进行横向比较,研究发现两款仿真软件前几阶模态分析结果比较接近,基本吻合,验证了该海上风电机组模型构建准确以及前几阶基础模态分析的准确性.同时模拟分析的研究结果表明,不同桩基情况土壤P-Y值整体倍率小范围改变对于整机基础频率的影响变化不大.     

齿轮系统非线性动力学特性分析

综合考虑齿侧间隙、时变啮合刚度、综合啮合误差等因素,建立了直齿轮副单自由度非线性动力学模型,并利用变步长Runge-Kutta法对单自由度运动微分方程进行了数值求解。结合系统的分岔图、相图、Poincaré映射图以及FFT频谱图,分析了系统在参数变化时的动力学特性,得到了系统的混沌运动规律。结合齿轮的动载荷历程,得到了齿轮啮合冲击状态在非冲击、单边冲击以及双边冲击状态之间变化时变化过程与系统参数之间的关系。     

非线性Jeffcott转子-滚动轴承系统动力学分析

为了研究Jeffcott转子-滚动轴承系统的非线性动力特性,建立了其非线性动力学方程,并用自适应Runge-Kutta-Felhberg算法对其求解。利用分岔图、Poincaré映射图和频谱图,分析了参数、强迫联合激励的Jeffcott转子-滚动轴承系统的响应、分岔和混沌等非线性动力特性。结果表明,Jeffcott转子-滚动轴承系统有多种周期和混沌响应形式,其振动频率不仅有参数振动频率成分和强迫振动频率成分,而且有二者的倍频成分和组合频率成分;Jeffcott转子-滚动轴承系统的非线性特性随着径向游隙的增大而加剧。     

Combustion dynamics in a model lean-premixed gas turbine with a swirl stabilized injector

Unsteady numerical study has been conducted on combustion dynamics of a lean-premixed gas turbine with a swirl injector. A three-dimensional computation method utilizing large-eddy-simulation (LES) technique with finite rate chemical reaction was applied with the message passing interface (MPI) parallel architecture. The unsteady turbulent flame dynamics are carefully simulated so that the flow motion can be characterized in detail, showing fairly comparable results with the experimental data. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots and large vortical structures in the azimuthal direction. The correlation between pressure oscillation and unsteady heat release is examined by the spatial Rayleigh parameter. In addition, it is shown that the complicate heat-release-structure can be precisely regenerated by means of modal analysis using proper orthogonal decomposition (POD).