When journal bearing works in large eccentricity condition, the thermal effect and elastic deformation will change the lubrication state, and then affect the friction characteristics.A mixed thermoelastohydrodynamic model was established, which coupled with elastic deformation, asperity contact, temperature distribution, viscosity-temperature and viscosity-pressure effect.The model was solved by finite difference method, and the pressure and temperature distribution in different working conditions were obtained.The influence of thermal effect and elastic deformation on lubrication state transformation and bearing performances parameters were analyzed.The experimental platform was built to measure the temperature distribution on the inner surface of the specimen, and the test results verified the correctness of the calculation model.The results show that the thermal effect and elastic deformation in large eccentricity make the oil film lubrication state change.The asperity contact produces more heat and the temperature achieves the maximum near the minimum film thickness.The larger contact pressure appears at both sides of the bearing due to thermal effect and elastic deformation.The load capacity and frictional force decrease after considering the thermal effect and elastic deformation.

The load capacity of ultrasonic levitation bearing has become an important factor limiting its practical application in engineering, due to which the load capacity is very small compared to that of other gas bearing. In order to obtain greater load capacity, surface texture is introduced into ultrasonic levitation bearing in this study. A theoretical model considering the geometry parameters and mode shape is established to obtain the running performance of surface-textured ultrasonic levitation bearing, which is solved by using eight-point discrete grid finite-difference method. Influence of driving voltage, rotational speed, eccentricity ratio, texture position, and texture size parameters on load capacity is investigated systematically. Previous experimental results were used to verify the feasibility of the proposed model. The results show that positive texture can effectively improve the load capacity of ultrasonic levitation bearing, especially under ultrasonic levitation mode. Research results are instructive for understanding the lubrication mechanism of ultrasonic levitation bearing and further promote the practical application of the bearing in engineering.

低速工况下处于混合润滑状态的滑动轴承易因变形或倾斜而发生磨损.为分析轴颈倾斜和磨损对滑动轴承混合润滑特性的影响,建立了计入轴颈倾斜和弹性变形的平均流量方程、G-T接触方程和Archard磨损方程耦合模型,采用有限差分法及超松弛迭代法计算混合润滑状态下轴承特性参数和时变磨损参数,对比了轴颈倾斜前后或磨损前后轴承的润滑性能,并分析粗糙度和边界摩擦系数等因素对各性能参数的影响.搭建摩擦磨损试验台测试了倾斜状态下轴承的润滑特性,验证了理论模型的正确性.理论分析与试验结果表明:重载大偏心时轴承转变为混合润滑状态,轴颈倾斜程度越大,轴承越容易发生混合润滑;轴承倾斜后,压力峰值和接触区域形状发生改变,磨损量因而发生变化,并且磨损深度分布沿轴向或周向倾斜;磨损降低了油膜的动压效应,并且使膜厚比降低,导致油膜压力峰值下降约20％,接触压力峰值降低约90％,承载力最高下降约19.71％;对比磨损前后的轴承形貌发现,轴颈倾斜使得磨损集中于间隙减小的一端.该研究可为实际工程中轴承的设计提供理论依据.

The conical bearing can withstand both journal and axial load because of the conical-shape fluid film, and an investigation concerning the thermodynamic lubrication and stability properties is proposed for a conical hydrostatic/hydrodynamic floating ring bearing theoretically and experimentally. The finite element method is coupled with the finite difference method to solve the variable-viscosity Reynolds equations, thermal energy equations, and the corresponding boundary conditions for the inner and outer films in a floating ring equilibrium state, and the conical bearing-rotor dynamic and stability performance models are built up with the perturbation theory and Routh-Hurwitz method. The primary characteristics parameters that are obtained under different operational conditions suggested that there presents a significant temperature gradient distribution over the lubricated domain, the thermal effects decrease the load carrying capacity, friction power loss, and stiffness and damping coefficients, and the viscous dissipation influences the variation of threshold instability speed with eccentricity and reduces its maximum value. In experiments, the temperature distributions of the oil leakage flow are measured to compare with the calculated results for the validation of the mathematic model using an infrared thermal imager, and the thermal effects need to be taken into consideration for the bearing lubrication analysis and design.

为研究计入黏温效应的径向滑动轴承紊流润滑特性,以某汽轮发电机径向滑动轴承为研究对象,基于FLUENT两相流模型建立计入黏温效应的高速、大功率、重载滑动轴承紊流润滑状态下的仿真分析模型;采用Creo软件建立三维油膜模型并导入ICEM软件划分结构化网格,通过编写的黏温方程UDF程序来定义润滑油黏度属性;基于建立的FULENT模型研究定黏度与变黏度条件下偏心率和雷诺数对轴承紊流润滑特性的影响,并将仿真结果与广泛应用的Ng-Pan紊流润滑理论结果进行对比,验证仿真结果的正确性.研究结果表明:考虑黏温效应后,轴承最大油膜压力、最大油膜温度显著降低,承载力、摩擦力有所减小,而摩擦因数、端泄流量有所增加.

The shaft misalignment under mixed lubrication is an important factor affecting the running performance of the bearing, which can occur under heavy load and unsatisfactory assembly. This paper presents a misaligned journal mixed lubrication model coupling for the asperity contact effect, elastic deformation, viscosity–temperature, and viscosity–pressure effect. The finite difference method was employed to calculate the model, and an experimental apparatus designed in this paper was used to test the friction and temperature characteristics of the specimens. The results show that the pressure field, film thickness, and elastic deformation of the bearing conformed to asymmetric distribution along the axial direction under misalignment conditions and there was a notable end side effect. In addition, the frictional force and side leakage flow were evidently enhanced with the increase in the inclination angle in a certain range. The experimental results showed that there was a visible wear phenomenon on the end sides of the bush and shaft. The research results are beneficial for understanding the mixed lubrication mechanism of misaligned journal bearing.

针对基于FLUENT软件计算滑动轴承存在需要调整偏位角而多次划分网格,导致计算效率低的问题,提出了一种改进算法,通过采用C++和动网格技术并编写UDF程序,实现了轴承静平衡位置偏位角的自动迭代.采用提出的计算方法对轴承油膜压力分布及静特性参数求解,并与理论数值计算结果进行对比,验证了计算模型的正确性,提高了计算效率.

针对挤压膜气体轴承悬浮力小的问题,将表面凸台引入挤压膜气体轴承,考虑表面凸台及轴承结构模态振型建立了时变及非稳态的挤压膜气体轴承运转特性分析模型,为解决凸台轴承气膜厚度分布不连续带来的求解困难问题,采用八点离散法对模型离散求解,进而开展该类轴承的承载特性分析.首先分析了光滑轴承和表面凸台轴承的气膜厚度和气压分布,然后分析了凸台参数、安装方式及运转方式对轴承承载特性的影响,结果表明:凸台的引入改变了气膜厚度的分布,提高了气膜压力峰值;悬浮力随台高、台宽、台数及驱动电压增大而增大;LOP型安装方式悬浮力大于LBP型;混合模式下的悬浮力大于纯挤压模式.

以径向动压轴承为研究对象,基于摄动法理论建立了计入周向表面波纹度下的扰动Reynolds方程,利用有限差分法和松弛迭代法对Reynolds方程、能量方程以及温黏关系式进行离散求解,计算了重载工况、不同波长下的压力场和温度场分布、无量纲承载力、端泄流量、摩擦力、偏位角等静特性参数,分析了低振幅周向表面波纹度对轴承润滑性能的影响机理,以及附加扰动压力随波长的变化关系.结果表明:在周向表面波纹度波长较大时,波长的变化对轴承静特性影响较大;在计算分析滑动轴承的润滑特性时,应计入表面波纹度和热效应的影响.

以动压滑动轴承为研究对象,建立了完全流体润滑模型和混合润滑模型.采用有限差分法进行数值求解,得到摩擦阻力、摩擦因数、承载力和端泄油温升等特性参数;通过膜厚比和摩擦因数判断轴承所处润滑状态,分析润滑状态转变后表面粗糙度对轴承特性的影响;并基于M2000型摩擦磨损实验机进行了混合润滑状态摩擦副跑合实验.结果表明,低转速下增大偏心率,轴承润滑状态从完全流体润滑转变为混合润滑,且综合表面粗糙度越大,润滑状态转变所需偏心率越小;混合润滑状态粗糙峰接触可以提高承载力,但导致轴承摩擦阻力和端泄油温升迅速升高;大偏心下实验结果与混合润滑理论计算结果基本一致.

以高速圆锥动静压轴承为研究对象,在油膜静、动特性有限元计算基础上建立同时考虑单位承载力下功耗、平均温升和失稳转速的多目标优化模型.根据工况要求,按照重要程度对各优化目标设定不同的加权系数,采用复合形法对优化模型进行了求解.结果表明,当半锥角和封油边宽度明显减小、浅腔包角减小时,圆锥轴承各优化目标均有所改善,单位承载力下功耗和平均温升得到了有效降低,失稳转速则得到提升.研究表明,通过对单位承载力下功耗、平均温升和失稳转速等优化目标设定不同的加权系数,可实现更低温升、更高转速或者更低功耗等设计目标.

在点接触EHL快速直接算法的基础上,提出按列分块、逐列求解的求解点接触EHL的新算法,以进一步减少计算量,提高计算效率.对新算法的精确性和高效性进行验证,并探讨新算法的参数适用范围.结果表明:新算法不仅具有更高的计算精度和计算效率,而且具有更宽的参数适用范围,在轻载工况、中载、重载工况下都可以得到很好的收敛解,是对点接触EHL求解快速算法的进一步改进和发展.

基于机械振动学和弹流润滑理论,将弹流油膜简化为弹簧阻尼,建立了线接触摩擦副的摩擦学、动力学耦合模型,用数值方法求解了摩擦副的振动响应,通过简谐激励下系统的阻尼环求得摩擦副的刚度和阻尼,分析了载荷、速度对摩擦副动力学特性的影响.结果 表明:弹流油膜具有显著的刚度、阻尼特征;弹流状态下,当速度一定时,摩擦副的刚度、阻尼随载荷增加而几乎线性地增加;而当载荷一定时,摩擦副的刚度、阻尼随速度的增加而指数般减小.

为提高圆锥动静压轴承的综合性能,以单位承载力下功耗最小和平均温升最低为优化目标,考虑几何结构约束条件,采用最优拉丁超立方进行设计空间的布点,进行有限元数值计算.基于计算结果,采用Kriging方法建立目标函数的近似代理模型.在此模型基础上,使用非劣分层遗传算法(NSGA-II)获得Pareto最优解集;最后通过权重系数法求得最优非劣解.结果表明:优化后方案1的两个目标函数值分别较优化前减小了18.8％和10％,优化方案2分别降低了10.9％、32％;轴承无量纲功耗有所降低、无量纲承载力得到提升,温升降低明显,轴承整体性能较优化前有较大提升.

Purpose This paper aims to study the influence of thermal effect on the performance for a high-speed conical hybrid bearing including stability and minimum oil film thickness. Design/methodology/approach A thermal hydrodynamic (THD) model and dynamic model of single mass rigid rotor system were established by taking conical hybrid bearing with shallow and deep pockets as the research object, dynamic coefficient and stability parameters of bearing-rotor system were obtained by using finite element method (FEM) and finite difference method (FDM) to solve computational models of Reynolds equation, energy equation and viscosity-temperature equation. Minimum oil film thickness was obtained based on bearing force balance. Dynamic coefficient was compared with previous findings. Findings After considering thermal effect, the dimensionless critical mass decreases, a significant decrease in the instability speed, and the stability of the system decreases greatly; the minimum oil film thickness decreases because of thermal effect. Originality/value The thermal effect is combined with dynamic characteristics to analyze stability of the rotor system for a conical hybrid bearing. Influence of thermal effect on minimum oil film thickness is studied. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2019-0542/

When the working surface roughness of hydrodynamic sliding bearing reaches the same magnitude (micron) as the oil film thickness, the influence of surface roughness on the characteristic parameters of bearing cannot be ignored. In order to study the influence of roughness on the static characteristics of bearing, an experimental platform was built based on M2000 friction and wear testing machine to test the sliding friction pairs of 42CrMo steel, and a Reynolds mathematical model considering the surface roughness was established. According them, the bearing capacity, friction resistance and friction coefficient of oil film with different surface roughness are obtained. The results show that the larger the roughness is, the larger the friction resistance and friction coefficient are. When the load is 400 N, the friction resistance of the specimen with the roughness of 0.312 µ m decreases 60.27% compared with the specimen with the roughness of 1.714 µm. When the roughness is 0.2 µm, the friction resistance of hydrodynamic bearing can get a smaller value.

为研究热效应对高速圆锥动静压轴承静特性的影响,建立具有深浅腔结构的圆锥动静压轴承的Reynolds方程、能量方程、深腔流量平衡方程及相关控制方程;采用有限元法和有限差分法对其进行离散,运用正系数法则对能量方程系数及常数项的离散系数进行处理,联立求解得到油膜压力分布与温度分布,计算出高速圆锥动静压轴承的静参数,并分析热效应对高速圆锥动静压轴承静特性的影响.结果 表明:热效应使高速圆锥动静压轴承油膜压力减小,且转速越大,压力减幅越大,油膜温升越明显;计入热效应后,润滑油黏度降低,引起高速圆锥动静压轴承偏位角增大,轴向、径向承载力减小,端泄流量增大,摩擦力减小,且转速越高变化越显著.

以径向浮环动静压轴承为研究对象,采用有限元法和有限差分法联立求解Reynolds方程、能量方程和温黏关系式,得到内外层油膜的压力分布、温度分布和黏度分布,对油膜压力积分得到轴承的刚度系数和阻尼系数.针对轴颈、浮环建立统一的动力学方程,结合能量方程和Routh-Hurwitz准则推导出单质量刚性对称浮环轴承-转子系统的热失稳判据,分析了油膜热效应对内外膜最小油膜厚度与失稳转速的影响.结果 表明:内外膜油腔呈现多个的温度峰值,两端面温度高于油腔中央温度;内外膜最小油膜厚度和系统失稳转速随着进油温度的升高而减小;高速工况下,油膜温升是导致浮环轴承发生油膜破裂和失稳现象的重要因素,计算时需计入油膜热效应对轴承性能的影响.

为研究表面粗糙度对动压轴承特性参数的影响,引入高斯分布,以随机粗糙模型为基础建立计入粗糙表面影响的动压轴承特性模型,采用有限差分法对模型进行联立求解,得到了油膜承载力、刚度系数、阻尼系数等特性参数随表面粗糙度改变的数值,着重分析了表面粗糙度对最小油膜厚度的影响.计算结果表明,动压轴承工作在小偏心率下时,表面粗糙度增大对轴承特性参数影响不大;大偏心率下,表面粗糙度增大会使油膜承载力增加,失稳转速降低,同时油膜厚度减小至临界值,极易产生磨损.文章对合理选取动压轴承表面粗糙度有参考价值.

There exist laminar and turbulent flow in the inner and outer fluid film of the hybrid floating ring bearing at high speed. The finite element method (FEM) and finite difference method (FDM) are used to solve the thermohydrodynamic (THD) lubrication model within the laminar and turbulent mixed flow regime which governs the pressure, temperature, viscosity, and Reynolds number of the two-layer fluid films together for a type of the journal hybrid floating ring bearing with deep/shallow pockets. The static and dynamic characteristics are analyzed including the load capacity, the friction moment, the volume flowrate, the stiffness, and damping coefficients with consideration of the mixed flow and thermal effect based on the floating ring balance. The unitized kinematic model of the shaft and floating ring is proposed to deduce the instability criteria and calculate the threshold rotational speed of a rigid Jeffcott rotor system supported on two hybrid floating ring bearings by the Routh–Hurwitz method. The results present that there are non-uniform pressure and temperature profile within the fluid film field, and the laminar flow and turbulent flow appear at certain positions of film through theory and experiment, separately. The mixed flow effect promotes the bearing load capacity and the friction moment at high speed and eccentricity, and the system threshold speed drops within the mixed flow regime. Therefore, the thermal effect and mixed flow existing in the fluid film should be considered into the lubrication analysis for the floating ring bearing.