风电齿轮箱两级行星齿轮传动系统的非线性动力学特性

考虑风电齿轮箱两级行星轮系传动系统各齿轮副的时变啮合刚度、综合啮合误差和齿侧间隙等非线性因素的基础上,建立了广义坐标下增速齿轮箱两级行星齿轮传动系统的动力学模型,采用变步长Gill积分法对该模型进行求解;采用分岔图、相图、FFT频谱图、poincaré截面图及最大Lyapunov指数图分析了激励频率和啮合阻尼比对系统振动响应及分岔特性的影响。结果表明:系统在多种非线性因素的耦合作用下会表现出丰富的非线性动力学行为,随着激励频率的增大,系统在混沌运动、拟周期运动和倍周期运动之间切换和变化,且退出混沌的方式多为倒分岔;在保证系统传动效率的前提下适当提高系统的啮合阻尼比,能够明显弱化和抑制系统的混沌运动,减小其振动幅度,对提高系统的稳定性具有一定的作用。     

基于有限元法的过盈配合接触特性分析

以某风力发电用齿轮箱为例,采用有限元法对斜齿轮与空心轴的三维弹性有摩擦接触问题进行了分析,针对不同工况、不同过盈量和摩擦系数下的过盈配合进行计算,获得了齿轮孔和轴之间接触压力和摩擦应力的分布随载荷、过盈量和摩擦系数的变化规律,为轴与轮毂之间合理过盈量的选择提供依据.     

大型风电齿轮箱系统耦合动态特性的研究

综合考虑轮齿啮合时变刚度、齿轮传递误差、齿轮啮合冲击以及风载变化等因素影响,建立具有多级齿轮传动的大型风电齿轮箱的齿轮-传动轴-轴承-箱体系统耦合非线性动力学模型。对风电齿轮箱系统有限元模型进行耦合模态分析,运用模态叠加法对齿轮箱系统在内部激励与外部激励综合作用下的振动响应进行求解。将仿真结果与实验数据对比,进而得到齿轮箱各点振动位移、速度、加速度及结构噪声等系统动态评价指标,为大型风电齿轮箱动态特性的准确评价及齿轮系统动态性能优化设计提供理论依据。     

计入结构柔性的风电齿轮箱行星轮系动力学特性研究

针对常规梁/壳单元无法考虑复杂构件几何特征、计算精度低和大规模有限元计算量大、系统级建模与动态分析困难的问题，提出一种计入结构柔性的行星轮系变速动力学建模方法。以某型5 MW级风电齿轮箱低速级行星轮系为研究对象，根据内齿圈结构及边界特征，采用有限元缩聚理论建立内齿圈轮齿与弹性支撑的耦合关系，通过引入啮合副变速表征变量和内齿圈虚拟振动线位移，将驱动轮转角与行星轮系多轮齿啮合状态进行关联，并计入行星架和太阳轮轴柔性，利用界面位移协调条件将各构件耦合，建立行星轮系变速动力学模型。研究结果表明，当5个行星轮受力平衡时，内齿圈轮齿节点瞬态变形整体呈“五角星”形状，并随着行星架旋转；行星轮系轮齿动载荷先增大后减小，变化趋势与单对齿啮合刚度相似；稳态工况下的内齿圈轮齿节点振动位移呈现大幅低频波动和高频振动的叠加特征；输入扭矩突变会破坏多个行星轮之间的动载荷平衡，而柔性内齿圈可在一定程度上吸收部分因冲击载荷引起的构件振动，提高了均载性能。     

风电机组塔筒模态的环境脉动实测与数值模拟研究

摘 要：基于随机振动及系统识别理论,对内蒙古京能乌兰伊利更风电场中三座风电机组塔筒进行了环境脉动实测,提出了 “桨叶—轮毂—机舱—塔筒”耦合的整体建模的方法,数值模拟与实测结果表明,风电机组塔筒可以有效地避免共振,满足GL规范的设计要求;塔筒主要振动形式为侧向弯曲振动、前后弯曲振动和扭转振动;塔筒一阶平动阻尼比为1.78%左右,一阶扭转阻尼比为0.6%左右。采用整体建模方法建立的模型与实测结果有较好的一致性,可以指导风力发电塔系统的风致动力响应分析和振动控制分析。     

基于小波包与倒频谱分析的风电机组齿轮箱齿轮裂纹诊断方法

为实现风电机组齿轮箱及时有效地监测和维护,提出基于小波包与倒频谱分析的风电机组齿轮箱齿轮裂纹诊断方法。该方法针对齿轮裂纹振动信号为转速频率对啮合频率及其倍频调制的特点,利用小波包分解来识别振动信号中的故障特征,通过小波包频带能量监测得到故障部位的啮合频率范围;考虑到倒频谱可以分离和提取难以识别的密集调制信号的周期成分,基于倒频谱识别故障部位的转速频率,综合利用两种频谱分析方法得到的啮合频率和转速频率,能诊断故障部位和类型。实验研究表明,该方法能精确地诊断齿轮裂纹故障,并可以实现对风电机组齿轮在复杂环境中退化状态的监测,预防断齿等重大故障的发生。     

盾构刀盘驱动三级行星齿轮系统固有特性及灵敏度分析

建立了三级行星齿轮传动系统的平移-扭转耦合动力学模型,模型考虑了时变啮合刚度、各级中行星轮位置相角的时变性、啮合综合误差、阻尼等影响因素。基于特征值问题求解了系统结构的固有频率和振型,并将其系统振动模式归为三类：扭转耦合振动模式、平移耦合振动模式、行星轮振动模式。研究了不同振动模式下固有频率对系统参数的灵敏度。研究结果表明,在一些系统参数敏感点处,参数的微小变化不仅导致固有频率灵敏度、模态能量的大幅变化,也将引起能量在各级间发生转移,使得振动特性剧烈变化。     

声子晶体平板组合成像特性分析

用多重散射方法分析了声子晶体单平板和多平板的成像特性。发现：在特定频率范围内,引入等效负折射率后,单板负折射成像可用反Snell定律描述;多层声子晶体平板成像服从依次成像规律,可类比传统几何光学中共轴球面系统的成像,引入实物实像、虚物虚像等概念;平板透镜不改变出射波的出射方向,仅使出射位置产生平移;多平板透镜的累加成像与等厚度的单一平板透镜成像具有相同的效果。平板透镜的这些成像特点,使其在成像质量、加工方法、系统组合等方面比球面透镜更具优势。     

海上风电机的抗台风设计

风电机组的制造成本和使用寿命取决于运行中的疲劳载荷、极端载荷和设计所依据的标准。目前,设计风电机组依据的大都是以欧洲环境特征为背景的标准,不加考虑地在台风地区使用会增加风险或制造成本。只有充分认识台风的气候特征和对风电机组的破坏机理,综合考虑,才能设计制造既能抗台风又能确保项目经济可行的风电设备。     

行星轮系动力学分析与响应表示方法研究

集中参数动力学建模是了解行星齿轮故障机理的有效手段,在利用集中参数模型仿真分析时,选择合适的变量表示系统的响应至关重要。针对现有方法不适于太阳轮固定的行星齿轮系统响应表示的问题,提出采用啮合线方向加速度直接叠加表示行星齿轮系统响应的方法,建立行星齿轮的平移?扭转模型;通过啮合线相对位移和啮合力信号及频谱分析,解释了三自由度选择的必要性,并验证了模型的正确性;与两种典型的响应表示方法比较,所提方法在齿轮正常和太阳轮故障时均具有较好的效果,可以有效提取啮合频率及故障频率;通过齿轮正常和太阳轮故障的实验信号频谱分析进一步验证了所提方法的合理性。     

The wear characteristics of thrust washer in conflux planetary gear train of power shift transmission

The wear between planet gear and thrust washer has been investigated based on the thrust washers in planetary transmission. The reasons leading to the wear failure are studied and the measurements for the reduction of abrasive wear are also exploited. A typical wear failure of thrust washer has been analyzed in terms of macromorphology observation, SEM observation of microstructure, material composition test, the metallographic analysis on radial cross section, and microhardness testing. Oil viscosity, oil contamination, and element spectra are analyzed and used to interpret the failure reasons. Through comprehensive analyses of metallographic structure and microhardness, the temperature distribution of thrust washer is obtained, which demonstrate that the adhesive wear is the main wear type for thrust washer although the fatigue wear is also observed. The most wear of thrust washer can be attributed to the great axial force during the working process, which leads to big contact stress. The high temperature at friction surfaces could surpass critical temperature and cause phase transition of austenite in the material. Inadequate cooling effect due to lack of lubrication oil is the main reason for high temperature caused by wear. Upon the comprehensive analyses, in the last section of this work some measurements are put forward for the reduction of the wear.     

风屏障对高架桥上列车气动特性影响机理分析

基于同步测压技术,以京沪高速铁路典型高架桥和CRH2列车为背景,研究风屏障对典型车桥组合状态下列车的风压分布和各面气动力分布特征的影响,以分析风屏障的气动影响机理,并从流体力学角度进行解释。研究结果表明:风屏障对上游列车气动特性影响较大,下游列车由于处于尾流中,受之影响较小;设置风屏障后,上游列车由于迎风面风压由正变负,使得该面的侧力与背风面相反,故使总体侧力减小,车顶平均风压显著减小,使得车顶升力约增大50%,背风面和车底风压变化较小;风屏障透风率及高度取值需根据具体环境进行优化,并需注意防风效果并不与减小平均风速等同。     

海上风机桩式基础结构形式综合模糊优选

针对海上风机基础设计中经常遇到复杂的方案优化选型问题,将多因素、多级模糊优选理论引入到基础的设计选型中。针对影响因素复杂、确定隶属函数主观因素较强的情况,成功引入因素的优先关系法来确定优选矩阵的隶属度,较好地解决了确定隶属函数的人为影响。通过此优选模型成功地将影响基础设计选型的13种主要因素和4种桩基基础设计形式进行了多级模糊综合优选决策,得到了比较理想的决策结果,为海上风机基础设计选型提供了新的思路。     

含摩擦力的行星齿轮传动系统非线性动力学模型

建立了一种考虑摩擦力、时变啮合刚度、齿侧间隙和综合啮合误差的2K-H型行星齿轮平移-扭转耦合非线性动力学模型。分析计算了啮合齿对间的相对位移,根据啮合区啮合齿对数不断变化的特点,推导出不同啮合齿对间摩擦力力臂计算公式,考虑了双齿啮合区的齿面摩擦力对齿轮系统振动的影响,推导了系统多间隙,变参数和多自由度的动力学微分方程组。最后运用变步长Gill积分法求解系统多自由度间隙型非线性微分方程组,得到了考虑滑动摩擦力影响时系统的振动响应。     

Foundations for offshore wind turbines

An important engineering challenge of today, and a vital one for the future, is to develop and harvest alternative sources of energy. This is a firm priority in the UK, with the government setting a target of 10% of electricity from renewable sources by 2010. A component central to this commitment will be to harvest electrical power from the vast energy reserves offshore, through wind turbines or current or wave power generators. The most mature of these technologies is that of wind, as much technology transfer can be gained from onshore experience. Onshore wind farms, although supplying 'green energy', tend to provoke some objections on aesthetic grounds. These objections can be countered by locating the turbines offshore, where it will also be possible to install larger capacity turbines, thus maximizing the potential of each wind farm location. This paper explores some civil-engineering problems encountered for offshore wind turbines. A critical component is the connection of the structure to the ground, and in particular how the load applied to the structure is transferred safely to the surrounding soil. We review previous work on the design of offshore foundations, and then present some simple design calculations for sizing foundations and structures appropriate to the wind-turbine problem. We examine the deficiencies in the current design approaches, and the research currently under way to overcome these deficiencies. Designs must be improved so that these alternative energy sources can compete economically with traditional energy suppliers.     

Stealth technology for wind turbines

Currently, a large proportion of proposed UK wind farms have either concerns raised at the pre-planning stage or formal objections made by radar operators on the basis of the potential for wind turbines to cause interference to radar systems. The current generation of on and off-shore three-bladed horizontal axis wind turbines have radar signatures consistent with their often very large physical size and hence considerable potential to reduce the ability of ground-based radars to detect targets in the vicinity of the farm. The impact of wind farms, particularly on ground-based aviation radars such as those operated for air defence and military and civil air traffic control purposes is likely to become particularly acute as European Union member governments strive to meet the requirements for energy generation under the Renewables Obligation. In addition, the increasing number of offshore wind farm projects proposed has the potential to cause interference to marine radars such as coastal vessel traffic services and those on-board vessels for navigational purposes. This study considers the options available for the reduction of turbine radar signature and presents solutions for each of the main external turbine components. The radar signature reduction approaches are based on existing technologies developed for aerospace stealth applications. However, the realisation of these for the purposes of reducing wind turbine radar signatures is a novel development, particularly in the solutions proposed. The reduction of wind turbine-induced radar interference is a growing area of research.     

大型风力机组远程智能监测与诊断系统的研究与开发

该文研究了大型风力机组的远程智能监测与诊断系统的关键技术问题,介绍了系统的开发情况。整个系统采用分布式架构,由数据采集与处理、实时数据存储、智能监测与诊断和人机交互4个子系统组成。智能监测与诊断子系统采用了知识库/推理机架构,推理机是一个自主开发的基于模糊Rete算法的模糊专家系统,知识库中存储了来源于风力机故障实验研究的常见振动故障的诊断知识。通过故障仿真,验证了整套系统的有效性。