3D Two-way Coupled TEHD Analysis on the Lubricating Characteristics of Thrust Bearings in Pump-turbine Units by Combining CFD and FEA

The thermal elastic hydro dynamic （TEHD） lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis （FEA）. But it is still a problem to conduct the computation by combining computational fluid dynamics （CFD） and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

Vibration Signals and Condition Monitoring for Wind Turbines

Rolling element bearings are critical parts of modern wind turbines as they carry the loads of the turning structure and the wind force. The stochastic nature of the wind loads makes it difficult to estimate the useful operational life of the bearings. Condition monitoring of these bearings in a real time environment could be very helpful in estimating their performance and in scheduling maintenance actions when a condition-based maintenance strategy is followed. This procedure can be successfully implemented by using vibration analysis in the time domain or in the frequency domain, giving useful results about the current condition of bearings and the location of potential faults. Permanently located transducers on proper positions on the bearings’ housings can be used in order to collect, process and evaluate real time measurements and provide information about the bearing’s performance. In this work, a test rig is utilized in order to evaluate the performance of rolling bearings. The results of the experimentation are satisfactory and the progress of fatigue failures can be predicted through vibration analysis techniques showing that implementation in real scale may be useful.

An exploration of frictional and vibrational behaviors of textured deep groove ball bearing in the vicinity of requisite minimum load

In case of lightly loaded radial ball bearings,failure mechanisms other than fatigue such as smearing of raceways due to increased frictional torque and vibrations often prevail.Hence,attempts have been made herein for reducing the frictional torque and minimizing the vibrations of a radial deep groove ball bearing employing surface textures at the inner race.Nanosecond pulsed laser was used to create texture(involving micro-dimples having different dimple area density)on the inner race of test bearings.Using an in-house developed test rig,frictional torque and vibrational parameters were measured at different speeds and light loads(i.e.in vicinity of 0.01C,where C is dynamic load capacity of radial ball bearing).Significant reduction in frictional torque and overall vibrations were found in the presence of micro-dimples on inner race at light loads irrespective of operating speeds.Even without satisfying the minimum load needed criteria for the satisfactory operation,substantial reduction in smearing marks was found on the races of textured ball bearings in comparison to conventional cases.

ACOUSTIC ANALYSIS OF HYDRODYNAMIC AND ELASTO-HYDRODYNAMIC OIL LUBRICATED JOURNAL BEARINGS

The purpose of the present paper is to investigate the effect of elastic deformation of bearing liner on the acoustic behavior of oil lubricated journal bearings.Analysis is performed for hydrodynamic（HD） and elasto-hydrodynamic （EHD） lubrications.Dynamic behavior and acoustical properties are investigated through an analysis of pressure fluctuation calculated from the Reynolds equation governing the flow in the clearance space of the journal bearing.This is solved numerically using the finite difference method with the successive over relaxation technique.In elasto-hydrodynamic lubrication,the finite element method with in iteration scheme is adopted to solve both Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell.The results show that the sound pressure level of the bearing is markedly influenced by the flexibility of the bearing liner,the viscosity of lubricant and the load applied to journal.HD analysis shows that the journal centre＇s orbit,from a disturbed position,converges to the static equilibrium position faster than EHD lubrication.The results of the present paper could aid in the design of low-noise rotor-bearing systems supported by oil lubricated journal bearings.

Physics-based data analysis for wind turbine condition monitoring

This article presents methodologies for improving wind turbine condition monitoring using physics-based data analysis techniques.The unique operating conditions of the wind turbine drivetrain are described,and the complex kinematics of the gearbox is analyzed in detail.The pros and cons of the current wind turbine condition monitoring system(CMS)are evaluated.To improve the wind turbine CMS capability,it is suggested to use linear models with unsteady excitations,instead of using nonlinear and nonstationary process models,when dealing the wind turbine dynamics response model.An analysis is undertaken of the damage excitation mechanisms cause for various components in a gearbox,especially for those associated with lower-speed shafts.Physics(mechanics)-based data analysis methods are presented for different component damage excitation mechanisms.Validation results,using the wind farm and manufacturing floor data,are reported.

柴油机隔振器配置对主轴承润滑特性的影响

以某大功率多缸柴油机为研究对象,采用EXCITE Power Unit软件建立隔振器−机体−曲轴的整机隔振系统弹流润滑仿真模型,对比分析机脚布置位置和隔振器刚度对主轴承润滑特性的影响。仿真结果表明:当机脚支撑跨度增加时,支撑位置的轴承孔位移和倾斜程度增加,主轴承粗糙接触压力升高,此时轴承合力降低,摩擦损失功和平均热载改善;当隔振器刚度提升时,主轴承润滑特性趋于改善,采用刚度方案二(刚度为7920 N/mm)时可获得较优润滑指标,继续提升刚度的收益有限。

大功率风机主轴滑动轴承研究现状及发展趋势

风电机组大型化步伐加快,核心零部件的可靠性对风机运行的影响越来越大。滑动轴承具有高承载、长寿命、易维护、可扩展、小体积等优点,对风机主轴承关键零部件的国产安全可靠替代水平提高具有显著作用和很大潜力。分析了大功率风机主轴滚动轴承存在的问题与主轴应用滑动轴承的优势,并详细论述了风机主轴滑动轴承设计、材料、润滑、试验验证等多方面的技术方法和应用现状,总结了大功率风机主轴滑动轴承存在的问题及未来的发展趋势,为大功率风电主轴承数字化设计与产业发展提供参考。

水润滑轴承衬套装配间隙对轴系振动的影响

水润滑尾轴承通常安装在美人架和尾轴管中,轴承衬套的安装间隙大小直接影响到轴承刚度,从而对轴系振动产生影响,极大程度影响到舰船隐身性能。通过试验验证过盈配合和间隙配合2种安装结构的轴承在静载条件下的摩擦特性与振动特性。结果表明,2种安装间隙下的水润滑轴承的摩擦扭矩的变化趋势一致,均随载荷的增大而增大,随转速的升高而减小,间隙配合轴承的扭矩大于相同工况条件下过盈配合轴承的扭矩;在振动性能上,间隙配合轴承的振动幅值大于过盈配合的轴承,且相比于过盈配合轴承有更大机率出现高频特征频率。在相同工况条件下,过盈配合的轴承的摩擦特性和振动特性均优于间隙配合的轴承。

基于声发射和支持向量机的滑动轴承润滑状态识别实验

为了对滑动轴承润滑状态进行高效快速准确地在线识别,设计搭建了滑动轴承润滑状态实验台及声发射测量系统,使用声发射技术和遗传算法优化支持向量机的方法对滑动轴承润滑状态进行了实验测试和分析识别。通过对声发射信号进行预处理,从时域、频域、信息熵等多方面提取和选择有效特征参数,将提取到的有效特征参数组合成特征向量用作支持向量机的输入并得到支持向量机分类器的识别结果;通过遗传算法对惩罚因子和核函数参数组合进行优化,获得最佳的润滑状态识别结果,总体准确率达到了93.3%。

斜齿轮啮合弯矩对风电齿轮箱行星轮滑动轴承瞬态润滑性能影响分析

风电齿轮箱行星轮滑动轴承常被设计为以行星轮内孔和销轴分别作为轴套和轴颈,然而斜齿轮啮合弯矩容易使行星轮与销轴之间产生轴线不对中,导致边缘接触风险高,影响运行寿命。以6 MW级传动链齿轮箱行星轮滑动轴承为研究对象,考虑滑动轴承径向载荷、弯矩以及转速的动态影响,建立了行星轮滑动轴承瞬态摩擦-动力学耦合模型,并以风电机组传动链SIMPACK动力学模型提取的行星轮动态啮合力与时变转速作为行星轮滑动轴承的载荷与运动边界输入,分析了斜齿轮啮合弯矩、输入扭矩和滑动轴承半径间隙对行星轮滑动轴承润滑性能的影响规律,并进行了实验验证。研究结果表明,行星轮动态啮合力及其产生的啮合弯矩会造成行星轮轴心位置与偏斜角产生动态循环变化,并且随着载荷的增加,行星轮滑动轴承油膜/固体接触压力与不对中弯矩会逐渐增大;减小行星轮滑动轴承半径间隙可以有效提高其瞬态润滑性能。

基于改进残差网络的风电轴承故障迁移诊断方法

针对风电轴承故障源域数据和目标域数据特征分布不同而导致的故障诊断精度偏低问题,提出一种利用改进残差神经网络进行风电轴承故障迁移诊断的方法。该方法将卷积核和池化核设定为与一维振动信号卷积运算相适应的尺寸,从振动信号直接提取轴承的故障特征;在一维残差网络中同时使用批量归一化和实例归一化,进一步增强模型的特征提取能力;在模型训练阶段,通过源域数据和目标域数据的多核最大均值差异构建新的损失函数,以提高模型在不同分布数据集上的迁移学习及分类能力。利用故障轴承实验数据对方法的有效性进行验证,结果显示,即使受到轴承变转速运行工况和故障振动信号含噪声干扰成分的双重影响,该方法仍然可提取出轴承故障的重要特征,并实现不同工况轴承故障的迁移诊断和准确分类,这对于发展复杂环境下的旋转机械智能故障诊断技术具有参考价值。

基于四维张量特征分解的风电机组轴承故障缺失数据恢复方法研究

针对风电机组轴承故障信息采集过程中数据缺失导致故障类型无法识别问题,提出了一种基于四维张量模型特征分解恢复缺失数据的方法。首先,基于转速、时窗、经验模态分解和时间4个维度构建四维张量;其次,通过加权优化算法实现张量填充,修补故障数据的缺失值;然后,对张量进行Tucker分解得到核心张量及因子矩阵;最后,基于梯度优化算法进行迭代优化得到最终核心张量及因子矩阵,并利用二者对四维张量进行重构得到恢复数据。采用实验数据和实际数据来验证提出方法的有效性和可靠性。结果表明:两组恢复数据的RMSE值分别为0.3169和0.0291,远小于4种对比方法的RMSE值。利用双稳态随机共振对2组恢复数据进行故障特征提取,信噪比显著提高,分别为-13.2647和-15.5212,进一步验证提出方法的准确性。

在役风力发电机组变桨轴承高黏润滑油脂附着状态下阵列涡流检测

为实现在役风力发电机组变桨轴承高黏润滑油脂附着状态下轮齿齿面的高效精准检测,采用仿形阵列涡流技术,研究不同线圈排布方式和提离距离对轴承轮齿齿面缺陷检测结果的影响。结果表明:Z字型和复合型线圈排布方式的边缘效应范围不同,复合型仿形探头较Z字型明显缩短;通过检测10.00 mm×0.50 mm×1.00 mm(槽长×槽宽×槽深)人工槽缺陷,得出内、外齿型轴承的提离距离极限分别为1.04 mm和1.43 mm;对在役风机轴承在表面有高黏润滑油脂条件下进行了试验验证,检测缺陷尺寸与位置结果准确,误差小于5%。该研究成果可为变桨轴承轮齿齿面在役状态下的监督检测提供技术支撑及新思路。

基于声学超材料的水润滑尾轴承系统承载与振动性能仿真

为提高水润滑尾轴承的减振降噪性能,提出基于声学超材料的新型水润滑尾轴承设计方案,研究声学超材料单胞带隙产生机理和结构承载性能。利用响应面与有限元方法对设计方案的单胞与超材料减振层进行结构优化,并对优化后的新型水润滑尾轴承系统进行承载和减振性能仿真研究。研究表明,与将内衬替换成超材料和在内衬和外衬之间设置超材料方案相比,在外衬与轴承壳之间设置超材料的方案具有更好的承载和减振性能。优化设计轴承方案满足承载能力需求,且在292.31 Hz~601.58 Hz处具有良好的减振效果。相比于传统轴承,超材料轴承具有更好的减振特性,振动最大衰减为98.48%。研究为低振动噪声水润滑轴承设计提供了新思路。

紊流润滑滑动轴承壁面压力脉动效应研究

壁面压力脉动是紊流润滑滑动轴承随机振动的主要激励源之一,建立紊流激励特性和轴承结构动力学响应之间的关联,对高转速、低黏度润滑滑动轴承的状态监测和故障诊断具有重要意义。为研究紊流润滑滑动轴承的壁面压力脉动效应,考虑流体油膜中存在逆压力梯度的影响,选用Rozenberg模型和广义Corcos模型表征壁面压力脉动的自功率谱和互功率谱,采用波数域模态叠加法求解滑动轴承紊流壁面压力脉动模型,分析滑动轴承在不同工况参数下壁面压力脉动的激励特性以及结构的响应特性。结果表明:低波数区域紊流脉动压力是轴承结构高频随机振动的主要因素;随着润滑油黏度的降低,高频范围内的轴承模态响应幅值增大,共振峰值附近产生较宽的频带和较高的振幅;随着轴颈转速和径向载荷的升高,紊流压力梯度增大,高频范围内的轴承模态响应幅值也随之增大。

润滑解决风电轴承失效方案的研究进展

风力发电机组作为长期户外运行的大型精密机械,在交变载荷、变风速、偏载等恶劣工况下容易出现轴承失效现象,导致其工作寿命往往低于设计使用寿命。在造成轴承失效的原因中,超过50%的轴承失效是由润滑故障造成的,减少润滑故障延长设备寿命,有助于提高风力发电经济效益。通过调研风电机组轴承失效的主要形式,如电蚀、白蚀、点蚀等,总结了当前润滑油脂解决或改善轴承失效的方法,并从润滑技术入手,总结得出如何预防轴承失效的结论,保证机械设备正常稳定运行,最后提出风电润滑需要解决的问题和未来发展趋势。

滑动轴承微动磨损引发不稳定振动研究

从轴承支架微动磨损角度开展某超超临界汽轮机高压转子不稳定振动故障机理研究。基于Archard方程,建立轴承在实际装配和载荷条件下微动磨损分析模型。结果表明:轴承瓦枕与支架之间采用球面配合方式,在该区域内出现局部应力集中。在不平衡力激励下,激振力通过油膜传递到轴瓦。长时间运行后,瓦枕和支架之间出现微动磨损。轴承防跳间隙和插销间隙增大后,轴承失去稳定性,导致带负荷过程中轴颈中心位移较大,振动出现波动。结合某汽轮机上发生的不稳定振动现象进行了分析,根据轴颈中心位置变化特征可评估轴承状态。

轮轨激扰下轨道车辆轴箱轴承振动与润滑特性分析

基于赫兹接触和弹流润滑理论建立了考虑轴箱轴承的轨道车辆模型,研究了轮轨激扰对轴箱轴承的振动特性和油膜刚度特性的影响规律。分别采用MATLAB/Simulink和UM软件建立了轴承动力学模型和轨道车辆模型,通过相互作用力实现二者的耦合关系。模拟了轴承和轮对的典型故障形式,并详细分析了这些故障对轴承的振动特性和润滑特性的影响。研究结果表明:润滑可以有效减小轴承的振动;轴承的局部故障将导致油膜刚度的增大,轴承故障和车轮扁疤都对润滑的影响较为显著;此外,轮轨激扰会降低轴承外圈的振动比率,但是会增大车辆其他部件的振动,对车体的振动几乎无影响。

风电机组齿轮箱用润滑油的流变特性

为对比不同类型风电齿轮箱润滑油的流变特性及润滑性能,利用球-盘点接触光干涉润滑油膜与摩擦力测量装置对不同类型润滑油(PAG油、PAO油和矿物油)的膜厚和摩擦系数进行测量,采用光干涉法测定了润滑油的黏压系数,并分析不同滑滚比和卷吸速度下润滑油摩擦系数的变化规律,结合最小膜厚明确了润滑状态与热效应机制,对比不同类型润滑油斯特里贝克曲线中摩擦系数的变化,分析其润滑性能优劣。结果表明:PAO油和PAG油动力黏度较小,受热效应的影响较小,矿物油受热效应影响最大;PAG油在较低载荷时几乎没有极限剪应力阶段,具有更好的剪切性能;相同工况下,PAG油的摩擦系数最小,润滑性能优于PAO油。

密封瓦引发振动及其与摩擦故障比较分析

某燃气轮发电机组振动受密封瓦进油温度影响较大。密封油温降低后,振动增大,振动变化与密封油温度变化之间存在滞后现象。为了分析该振动机理,基于短轴承理论建立了密封瓦油膜力求解模型,基于热平衡理论建立了密封瓦截面温度梯度求解模型,计算分析了油温、偏心率、涡动幅度等对截面温度梯度的影响。研究发现,密封瓦间隙内油的剪切流动会在转轴上产生温差。温差受油温和偏心率影响较大,受涡动幅度影响较小。油温升高和偏心率减小后,截面温差减小。与摩擦故障相比,因为涡动幅值对温度梯度的影响较小,虽然振动会随密封油温变化,但没有出现振动周期性波动和发散现象。研究结论比较好地解释了这类不稳定振动现象。