叉车前桥动力吸振器的有限元及试验分析

针对某型号叉车前桥的振动特性,设计了一种以橡胶为弹性阻尼元件的被动式动力吸振器,为便于预测吸振器力学特性,建立了以橡胶为弹性阻尼元件的该种吸振器的有限元模型,该有限元模型的分析结果与实际测试的频响曲线吻合,在该吸振器安装在某型叉车上之后,前桥处的振动幅值比未安装吸振器前的振动值明显减小.     

拓扑优化技术在提高动力总成一阶弯曲模态频率中的应用

某混合动力客车动力总成一阶弯曲模态频率较低,致使车辆在正常运行过程中发动机二阶激励和电机激励均能激起动力总成弯曲共振的发生.对该动力总成进行了模态测试和有限元分析.结果表明,该动力总成合成箱部分结构刚度明显不足.采用拓扑优化技术针对合成箱进行了结构优化设计,使动力总成一阶弯曲模态频率由75Hz提高到116Hz,满足了设计要求.     

动力机械动力吸振器数值优化分析

以单缸柴油机为例研究了动力吸振器动力参数的优化设计问题。传统动力吸振器动力参数设计都是在简谐激励下进行的,经理论分析动力吸振器动力参数的设计与激励频率有关,所以对于非简谐的激励确定动力参数则比较困难。以实现平台最小位移响应为目标,通过数值仿真来确定非简谐激励情况下动力吸振器的动力参数。数值仿真结果表明：数值优化方法具有很好的精度。     

拉索式小型风力发电机塔架结构吸振器的研发

风力发电机塔架结构的自然频率与风轮的工作频率(风叶的通过频率)相近时,将发生共振,导致风力发电机无法正常工作。文章基于动力吸振原理,建立了拉索式小型风力发电机塔架结构等效振动模型,再以6kW级拉索式小型风力发电机塔架结构的缩小模型为对象制作吸振器,用理论与试验验证吸振器的有效性。试验结果表明,吸振器能够有效减少塔架结构共振频域内的振动。     

高速柴油机复合式减振器的试验研究

为了详细考察复合式减振器的减振效果,设计了一种可调频的动力吸振器,在一台直列6缸车用柴油机上进行了试验。研究中开发了轴系的扭、纵、弯三维振动的测试装置,测量了动力吸振器在几个主要弯曲调谐频率下曲轴前面自由端的三维振动,并与原机进行了对比。通过对试验结果的分析,发现采用匹配合适的弯曲减振器能够有效降低曲轴的弯曲振动,抑制曲轴的纵向振动。     

基于声学黑洞结构的附加吸振器设计与开发

声学黑洞(ABH)结构能够降低弯曲波波速,实现对结构中弯曲波的控制。基于声学黑洞的这一特性,设计开发了一种基于声学黑洞结构的附加吸振器(简称吸振器),分析了其抑制振动和吸收能量的特性,探讨了不同结构参数和连接方式对其性能的影响,并验证了这种结构在板件结构振动控制领域的应用效果,此研究具有重要理论意义和工程应用价值。     

连续悬臂梁动力吸振器的模型研究

针对吸振器动力参数固定不可变或仅能产生离散变化的局限性问题,在连续悬臂梁的基础上通过增加滑动质量块的方式,设计了一种新型的参数可连续变化的悬臂梁吸振装置,并对其进行了共振频率、效果试验分析.为提高主体振动控制的效果又对参数进行了优化分析.结果表明,该装置对受固定频率简谐激励的主体结构进行动力吸振可行有效,动力参数连续可调.     

多维耦合双层隔振系统动态吸振器吸振特性

建立了针对多自由度动态吸振器作用于多维耦合双层隔振系统上的六自由度动力学模型,给出了系统的量纲为1参数控制方程和系统力传递率表达式.基于此,研究了吸振器固有频率比、耗散系数、安装距离、安装跨度、质量比和转动惯量比对吸振器吸振特性(系统力传递率)的影响;并结合对系统模态能量分布情况的分析,阐明了吸振器的吸振机理以及最优参数取得条件;最后,结合内燃动车动力包这一工程对象,给出了其散热器子系统充当双层隔振系统吸振器用于提高系统在发动机停机工况的隔振性能应用实例.研究结果对于双层隔振系统多自由度吸振器参数的设计具有指导意义.     

重型自卸车动力总成悬置优化设计

为降低重型自卸车底盘振动,提高乘坐舒适性,建立了动力总成四点悬置系统模型.利用打击中心和能量解耦理论对悬置软垫的位置及刚度进行了优化,计算并分析了优化前后动力总成悬置系统的模态频率及能量分布.优化后动力总成悬置系统模态频率有效地避开了发动机的怠速激励从而避免了共振,同时各自由度下的解耦率也大幅提高.通过定置试验对优化方...     

自由活塞式斯特林制冷机吸振器部件优化设计

对自由活塞式斯特林制冷机的吸振器部件进行理论仿真分析和结构优化设计。结构优化设计主要从吸振器的配重块布局、固定螺母配置、阻尼特性等3方面开展。通过调整配重块的非中心对称分布，改善吸振器部件的1、2阶模态偏差，避免吸振器部件的翻转运动对吸振性能产生影响；通过对吸振器表面喷涂阻尼材料，改善其阻尼特性，提升吸振效果。开展整机振动测试，测试结果表明优化后的整机振动幅值为优化前的1/5，优化设计效果明显。     

Active tuned mass damper for damping of offshore wind turbine vibrations

An active tuned mass damper (ATMD) is employed for damping of tower vibrations of fixed offshore wind turbines, where the additional actuator force is controlled using feedback from the tower displacement and the relative velocity of the damper mass. An optimum tuning procedure equivalent to the tuning procedure of the passive tuned mass damper combined with a simple procedure for minimizing the control force is employed for determination of optimum damper parameters and feedback gain values. By time domain simulations conducted in an aeroelastic code, it is demonstrated that the ATMD can be used to further reduce the structural response of the wind turbine compared with the passive tuned mass damper and this without an increase in damper mass. A limiting factor of the design of the ATMD is the displacement of the damper mass, which for the ATMD, increases to compensate for the reduction in mass. Copyright © 2016 John Wiley & Sons, Ltd.     

Vibration suppression of a floating hydrostatic wind turbine model using bidirectional tuned liquid column mass damper

We propose to mitigate the barge pitch and roll motions of floating hydrostatic wind turbine (HWT) by combining the advantages of the bidirectional tuned liquid column damper (BTLCD) and the tuned mass damper (TMD). This is achieved by enabling the container of the BTLCD to move freely, connecting it to the main structure through springs and dampers, creating what we call a bidirectional tuned liquid column mass damper (BTLCMD). The BTLCMD is made by the hydraulic reservoir of the HWT, saving costs by avoiding the addition of extra mass and fluids. The HWT simulation model is obtained by replacing the geared drivetrain of the NREL 5‐MW barge wind turbine model with a hydrostatic transmission drivetrain. The dynamics of the BTLCMD are then incorporated into the HWT. Two simplified mathematical models, describing the barge pitch and roll motions of the HWT‐BTLCMD coupled system, are used to obtain the optimal parameters of the BTLCMD. Simulation results demonstrate that the BTLCMD is very effective in mitigating the barge pitch motion, barge roll motion, and the tower base load. The BTLCMD also largely outperforms the BTLCD in suppressing barge motions.     

Passive control of wind turbine vibrations including blade/tower interaction and rotationally sampled turbulence

This paper investigates the use of a passive control device, namely, a tuned mass damper (TMD), for the mitigation of vibrations due to the along‐wind forced vibration response of a simplified wind turbine. The wind turbine assembly consists of three rotating uniform rotor blades connected to the top of a flexible uniform annular tower, constituting a multi‐body dynamic system. First, the free vibration properties of the tower and rotating blades are each obtained separately using a discrete parameter approach, with those of the tower including the presence of a rigid mass at the top, representing the nacelle, and those of the blade including the effects of centrifugal stiffening due to blade rotation and self‐weight. Drag‐based loading is assumed to act on the rotating blades, in which the phenomenon of rotationally sampled wind turbulence is included. Blade response time histories are obtained using the mode acceleration method, allowing base shear forces due to flapping motion for the three blades to be calculated. The resultant base shear is imparted into the top of the tower. Wind drag loading on the tower is also considered, and includes Davenport‐type spatial coherence information. The tower/nacelle is then coupled with the rotating blades by combining their equations of motion. A TMD is placed at the top of the tower, and when added to the formulation, a Fourier transform approach allows for the solution of the displacement at the top of the tower under compatibility of response conditions. An inverse Fourier transform of this frequency domain response yields the response time history of the coupled blades/tower/damper system. A numerical example is included to qualitatively investigate the influence of the damper. Copyright © 2007 John Wiley & Sons, Ltd.     

基于TMD的海上漂浮式风力机稳定性研究

海上漂浮式风力机的稳定性研究已逐渐成为风电研究的重点与热点。以NREL(国家可再生能源实验室)5 MW风力机及ITI Barge平台为研究对象,建立海上漂浮式风力机整机模型,通过配置TMD(调谐质量阻尼器),研究其对环境载荷作用下的海上漂浮式风力机稳定性的控制效果。结果表明:TMD对漂浮式风力机塔架和平台的运动响应有明显的抑制效果,在TMD控制下,漂浮式风力机塔顶左右位移最大值降低近50%,稳定性提高38%;对漂浮式风力机平台的横摇及横荡运动控制效果较明显,平台横荡稳定性提高18%,横摇稳定性提高41%。     

基于动力学的某柴油机曲轴系扭振分析

采用动力学方法,建立了一个包括减振器和飞轮的某柴油机曲轴系扭振分析模型。着重进行了减振器频率的选定,并对选定减振器频率后的曲轴系扭振行为进行了仿真分析。结果表明,该轴系的扭振指标均在可接受的范围内,扭振行为较好。     

Structural vibration of tuned mass damper-installed three-span steel box bridge

To reduce the structural vibration of a three-span steel box bridge, a three-axis–two degree of freedom (DOF) system is adopted to model the mass effect of the vehicle; and the kinetic equation considering the surface roughness of the bridge is derived based on the Bernoulli–Euler beam ignoring the torsional DOF. The effects of tuned mass damper (TMD) on the steel box bridge show that the system is not efficient in reducing the maximum deflection, but it does efficiently reduce the free vibration of the bridge. It proves that the use of TMD on the bridge brings more efficiency in controlling the dynamic amplitude rather than the maximum static deflection.     

梯级泵站管道TMD振动控制仿真与减振优化

为了解调谐质量阻尼器(TMD)的减振效果,以某灌区泵站输水管道为例,全面分析TMD减振系统对管道结构的减振效果,以寻求最佳减振方案。结果表明,TMD减振系统可有效降低管道振动幅值;在适宜的质量比范围内,TMD减振效果相似;等质量情况下,单个TMD和两个TMD减振装置减振效果基本一致,因此在减少大质量附加质量对主结构自重的影响下,实际应用中宜分成等质量的多个减振装置,以达到较好减振效果;TMD装置布置在激励源附近或发生振动较明显的部位可高效减振。研究成果为大型管道结构振动原因分析和TMD减振控制产品研发提供了依据。     

汽轮机叶片结构阻尼研究发展现状及展望

叶片的安全一直是保证汽轮机正常运行的关键.随着汽轮机组单机功率的增大,尤其是近来超超临界机组的发展,末几级叶片越来越长,相应地降低了叶片的刚性,不但使叶片运行时扭转恢复角增大,也降低了叶片抵抗振动应力的能力,采用各种阻尼结构以提高叶片抵抗振动疲劳的能力是各个汽轮机制造厂家广泛采用的方法.在广泛收集有关研究资料的基础上,首先总结了汽轮机叶片中广泛采用的摩擦阻尼理论及试验研究成果,然后介绍了碰撞阻尼结构尤其是一种新的具有自调谐作用碰撞阻尼的一些机理及应用情况.最后对进一步研究汽轮机叶片干摩擦阻尼和碰撞阻尼提供了一些看法.     

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well-known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their rolling contact fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well-known that these premature failures are attributed to surface damages such as white surface flaking (WSF), white etching cracks (WECs) and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied to demonstrate their TTR mitigation capabilities. Then, a novel idea of open-loop high-speed shaft mechanical brake control is proposed. The results presented here show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high-speed shaft and reducing the risk of bearing slip by actuating the high-speed shaft brake at the onset of the transient event. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time applied to it. This novel approach allows the wind turbines to protect the gearbox bearings from TTRs using the existing hardware on the turbine.     

基于TMD的风力机塔筒振动控制研究

针对风力机塔筒在风振效应下振动过大的问题,该文基于调谐质量阻尼器(TMD)开展对风力机塔筒的减振控制研究。以某大型2 MW风力机塔筒为研究对象,基于ANSYS建立柔性的风力机塔筒有限元模型,并基于Kaimal谱和模态脉动曳力功率谱模拟得到脉动风速时程和风载时程曲线。为取得较好的TMD减振控制效果,根据Den Hartog法得到TMD的最优频率比和阻尼比。为分析TMD对塔筒结构强度的影响及其TMD的振动控制效果,对风力机塔筒进行静力学和风载作用下的动力响应仿真分析。研究结果表明:TMD对塔筒的静强度影响较小,相比于将TMD放置于塔筒内部,将TMD放置于塔顶机舱内能更有效地减小塔筒在风振效应下的位移峰值、标准偏差以及瞬态应力峰值,其抑制率分别达到63.51%、63.38%和59.74%。