大型动静力径向可倾瓦轴承热弹流体润滑研究

用有限元素法建立瓦块3维弹性变形计算模型。针对小包角瓦块支点非均匀布置方式及下方瓦块设有高压油顶起油囊的大型低速重载动静力润滑径向可倾瓦轴承,研究了由于瓦块3维弹性变形对轴承热动力润滑性能的影响。结果表明,在低速重载条件下需要考虑瓦块的弹性变形对动静力可倾瓦轴承热动力润滑性能的影响。     

刚性和弹性支撑可倾瓦推力轴承稳态特性分析

建立刚性球头支撑和弹性橡胶垫支撑可倾瓦推力轴承热弹流耦合模型；在弹性橡胶垫支撑可倾瓦推力轴承橡胶垫的弹性变形分析中采用了变形协调矩阵方法，以协调匹配橡胶垫变形和水膜厚度分布，同时在搜索稳态解的过程中引入模拟退火算法；基于变分原理求解Reynolds方程，得到了轴承水膜压力分布，并比较2种推力轴承在转子存在角不对中时的静特性。结果表明：理想工况下，刚、弹支可倾瓦推力轴承稳态特性没有明显区别；当转子存在不对中时，刚性球头支撑可倾瓦轴承在不同瓦块之间受力偏载严重，进而导致瓦面最小水膜厚度过小，瓦块容易出现磨损，而弹性支撑瓦不同瓦块之间水膜力分布更均匀，利于轴承的长期可靠运行。     

线切割一体化滑动轴承的静态性能研究

提出一种新型线切割一体化径向滑动轴承,该轴承瓦块在载荷的作用下能够围绕轴承座上的固定支点作微小弹性变形和摆动,具有可倾瓦轴承的特点。根据润滑理论,建立该新型线切割一体化径向滑动轴承的数学模型;采用Fortran与Ansys混合编程的方式,编制线切割一体化径向滑动轴承的动力学性能计算程序;考虑支座变形和瓦块变形的影响,考察偏心率、轴颈转速和支点几何尺寸对轴承单瓦块静态性能的影响。结果表明:轴承轴瓦受到的负载和最大压力随转速和偏心率的增大而增大,随支撑高度的增大而变小;轴瓦支点和半径方向的变形随转速和偏心率的增大而增大,其对轴承性能的影响不能忽略。     

汽轮机可倾瓦轴承油膜特性研究

为了研究汽轮机可倾瓦轴承的油膜特性,采用Pro/E建模和ANSYS模拟,选用计算三维模型的湍流SST模型,考虑到瓦块间隙及瓦块相互之间的影响,分析并比较不同瓦数可倾瓦轴承油膜流场的变化,得到可倾瓦油膜特性规律:对于某个瓦块,每个瓦块上的油膜形成一个正压极值中心,且随着瓦块数增加,极值中心向轴瓦支点处偏移,使瓦块上形成两个压力极值。瓦块温度分布较平稳,油膜出口处温升较大;随着可倾瓦瓦块数增加,油膜压力峰值逐渐减小且瓦块之间的油膜压力峰值差减小并趋于平稳,不同轴瓦间油膜温度变化较小。润滑油温升对油膜影响较大,汽轮机运行中可倾瓦四瓦轴承比较稳定,但应严格控制润滑油温升。     

推力轴承斜面平台瓦结构参数对弹性变形的影响

应用MATLAB软件对不同结构推力轴承斜面平台瓦块的弹流润滑性能进行数值计算分析。结果表明:弹性变形使轴承内压力分布缓和,水膜厚度变大,局部最大压力降低;推力轴承长宽比接近1∶1时,轴承变形较小;载荷不同,使轴承的变形量最小的最佳外内径比也不相同。     

推力轴承支承方式及间隙影响研究

研究了推力轴承支承方式及油膜间隙对推力轴承性能的影响,利用Newton-Raphson法编制差分计算程序,求得了推力轴承Reynolds方程和二维能量方程的数值解,得到了不同支撑方式下瓦块的油膜厚度、压力分布和温度分布。计算结果表明,点支承扇形瓦推力轴承的热力学性能要好于线支承扇形瓦推力轴承,同时支承处的油膜厚度对瓦块的承载能力影响很大。可以通过控制每个瓦块支承处的油膜厚度,避免推力轴承内部偏载的发生,降低推力瓦块的最大温升。     

可倾瓦轴承的完整动力分析模型及计算方法

提出求解可倾瓦径向滑动轴承完整动力特性的解析模型和计算方法,给出可倾瓦轴承完整动力特性系数矩阵的简明表达形式.基于瓦块和轴颈间的运动耦合关系,建立瓦块局部坐标系统.与瓦块和轴颈运动相关的全局广义位移矢量可以通过简练的步骤转换为局部动坐标系下轴颈的位移矢量;利用求解固定瓦轴承动力特性的方法求得的局部动坐标系下的油膜力及其Jocabian矩阵,该油膜力矢量可以精确地转换为全局广义坐标系下的表达形式.在轴承的平衡位置处,全局坐标系下的油膜力矢量关于广义位移和广义速度的Jocabian矩阵为轴承完整动力特性系数矩阵的负值.给瓦块一个设定的扰动频率,就可以得到简化的当量动力特性系数矩阵.此解析方法求解简单方便,可用于分析可倾瓦轴承-转子系统.     

大型重载推力轴承热弹流计算及尺寸效应

针对考虑热弹变形的大型重载推力轴承性能预测和尺寸效应问题,对某大型重载推力轴承进行热弹流计算,研究轴承性能随极端载荷与尺寸的变化规律。介绍可倾瓦推力轴承热弹流模型的基本方程,通过计算得到不同尺寸和比压下的轴承性能数据,讨论大型重载轴承的尺寸效应。结果表明:案例轴承瓦块最高油膜压力应远离瓦尖,靠近瓦块支点,该设计有利于压力分布均匀而提高承载力;对于大尺寸推力轴承,由于变形的影响,当载荷超过某一限制值后,轴承性能会随着载荷的稍微增加而发生剧烈变化,甚至导致烧瓦失效。为了避免该现象出现,推力轴承设计时应该进行最大许用比压校核;对于大型重载,还需进行瓦块弹性支撑或平衡梁等均载结构设计。     

可倾瓦气体动压轴承承载能力的数值分析

应用MATLAB的偏微分方程工具箱,采用有限元法求解气体润滑Reynolds方程,通过完全装配分析法计算了可倾瓦动压气体轴承的承载能力,研究了轴承偏心和瓦块预负荷对可倾瓦轴承的承载能力、最小气膜厚度和最大气膜压力以及瓦块摆角的影响。计算结果表明,随轴承偏心或瓦块预负荷增大,各瓦块的承载能力和摆角发生明显变化,轴承的最小气膜厚度减小,最大气膜压力增大,承载能力增大。从理论上解释了可倾瓦轴承的承载能力与轴承偏心和瓦块预负荷的密切相关性。     

高功率密度柴油机连杆大头轴承润滑特性分析

基于全局 Newton-Raphaon 方法和柔度矩阵法对高功率密度柴油机连杆大头轴承的润滑性能进行数值摸拟;耦合求解 Reynolds 方程和弹性变形方程,比较弹性变形的连杆大头轴承与刚性轴承的轴心轨迹与压力分布。结果表明：将全局 Newton-Raphaon 方法与柔度矩阵法结合起来,对高功率密度内燃机连杆大头轴承的弹流润滑进行分析,解决了轴承偏心率大于1时弹流润滑计算难于收敛的问题;考虑表面弹性变形的连杆大头轴承与刚性轴承相比,在最大气体爆发压力附近,油膜压力分布的形状和大小明显发生变化,特别是在轴承的两端处,油膜压力明显增加并接近轴承中间部分的压力。     

Thermoelastohydrodynamic analysis of the static performance of tilting-pad journal bearings with the Newton–Raphson method

Thermoelastohydrodynamic lubrication (TEHD) analysis is presented to investigate the static performance of tilting-pad journal bearings. A completely numerical solution is obtained. The Newton–Raphson method is employed to predict the bearing characteristics of the hydrodynamic pressure, the eccentricity and the pad attitude angles simultaneously. For the temperature calculation, three-dimensional (3D) energy equations for the fluid under each pad and 3D heat transfer equations for the pads are solved using a sequential sweeping method. The elastic deformation and thermal expansion of each pad are calculated with the 20-node isoparametric finite element method. It is found that the Newton–Raphson method is a smart and efficient method. The results show that the elastic deformation due to the hydrodynamic pressure and the influence of the temperature elevation play an important role in the calculated bearing system.     

影响弹簧支承式推力轴承性能的几个因素

本文对弹簧支承式推力轴承进行了三维热弹流研究,发现变形量对轴承性能有很大影响,为此,着重分析了决定轴承变形和油膜形状分布的几个因素对轴承性能影响情况,研究表明,弹簧布置方式,轴瓦厚度和型面形状能严重改变轴承性能,在进行轴承设计时必须对上述因素进行了优化,并提出了一些优化建议。     

卧式水电机组用径向滑动轴承热弹流特性分析

研究轴颈挠度和瓦块表面热弹变形对卧式水电机组径向滑动轴承静态润滑性能的影响。推导考虑轴颈挠度和轴瓦热弹变形后的油膜厚度表达式;用中心差分法结合ANSYS软件联立求解雷诺方程、能量方程、固体热传导方程、密度方程、黏度方程和轴瓦热弹变形等,得到径向滑动轴承的热弹流润滑(TEHD)特性,并与不计入轴颈挠度及轴瓦热弹变形的油膜动压润滑特性进行比较。结果表明:在考虑轴颈挠度和轴瓦瓦面热弹变形的影响后,油膜压力、温度、厚度沿着轴承宽度中心线的对称特性消失;油膜压力峰值增大,峰值点位置由轴向中心区偏移至出口区;油膜温度峰值增大,最高温度发生在出口区;润滑区内的最小油膜厚度大幅度减小,油膜最小厚度处于出口侧边界附近;轴承润滑流量减小,损耗略有增大;轴承稳态运行时,轴颈偏位角基本一致。     

轴瓦弹性变形对固定瓦-可倾瓦组合径向滑动轴承润滑特性的影响

采用一种新型耦合算法,将有限差分法和3D有限元法综合应用于求解油膜压力和轴瓦弹性变形过程中。与其他算法相比,该算法更为科学、合理,同时具有收敛快、精度高的特点。通过对固定瓦-可倾瓦组合径向滑动轴承的研究,分析轴瓦弹性变形对油膜厚度、油膜压力、油膜承载力、摩擦阻力及轴承端泄量等润滑性能的影响。研究结果表明,在大偏心率的情况下,轴瓦弹性变形对轴承润滑性能影响较大。     

Time-dependent TEHL solution to centrally supported tilting pad bearings subjected to harmonic vibration

The bearing performance of a centrally supported tilting square pad, subjected to harmonic vibration, is analysed numerically. Thermo-elastohydrodynamic lubrication analysis considers simultaneously the heat transfer, elastic deformation of the pad's working surface, side leakage, and the inlet pressure build-up effect. Governing equations with their boundary conditions are transformed into non-dimensional forms so that the problem's non-dimensional parameters are obtained. An efficient procedure is developed to solve the problem numerically. By idealizing the pad as a uniform plate, a compliancy coefficient matrix is established to calculate the pad's surface deformation due to various pressure distributions. At each time step the pressure is obtained by a fast Newton-Raphson method, whereas the temperature is determined by an efficient finite difference approach. A dynamic parameter is introduced to describe the effect of the pad's periodic motion, which is found to be as important as the wedge effect when the dynamic parameter approaches unity.     

Thermoelastohydrodynamic Analysis of Fixed Geometry Thrust Bearings Including Runner Deformation

A thermoelastohydrodynamic theory for the analysis of sector thrust bearings is presented. The analysis includes the generalized Reynolds equation and a fully elliptic three-dimensional energy equation in the film. In addition, full three-dimensional heat transfer is allowed in the pad while axisymmetric conduction is allowed in the runner. Three-dimensional elastic deformation due to mechanical and thermal loading is allowed in the pad while axisymmetric mechanical elasticity is allowed in the runner. The performance of a parallel tapered-land thrust bearing including runner deformation effects is analyzed as a function of different models. It is seen that mechanical deformation of the pad affects the operating characteristics only slightly while thermal deformation of the pad can cause large increases in operating temperature. The runner deformation effects can include a reduction of the maximum film temperature at slight deformation or a large increase in film temperature at the inner radius of the pad at larger deformations.     

A mixed elastohydrodynamic lubrication model with layered elastic theory for simulation of chemical mechanical polishing

Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate.     

Effect of bearing pad deformation on the performance of finite fixed-pad slider bearings

The load support and other performance characteristics of any bearing depend on its film thickness profile which can be significantly affected by elastic deformations. The effect of bearing surface deformation on the static performance of slider bearings is reported. Deformation of bearing pads was calculated by three-dimensional elasticity equations using a finite element method.To generalize the study, a non-dimensional deformation coefficient relating the geometrical parameters of bearing pad, the clearance space, the elasticity coefficient of the pad material, the lubricant viscosity and the velocity of the slider is defined. The static characteristics are calculated and compared for different values of the deformation coefficient. The effect of Poisson's ratio v of the pad material on the performance of a slider bearing for steel (v = 0.3) and brass (v = 0.4) as pad materials is reported.     

Average flow model with elastic deformation for CMP

We present a three-dimensional (3D) average flow model considering elastic deformation of pad asperities for chemical mechanical planarization. To consider the contact deformation of pad asperities in the calculation of the flow factor, 3D contact analysis of a semi-infinite solid based on the use of influence functions is conducted for computer-generated rough surfaces. The average Reynolds equation and boundary conditions of both force and momentum balance are used to investigate the effects of pad roughness and external pressure conditions on a film thickness and wafer position angles. It is found that the position angles decrease with the increasing of the applied pressure and the roughest pad has the highest position angles at any given load. Comparing elastic and rigid pads, the minimum film thickness formed between the elastic pad and the wafer is thinner than that between the rigid pad and the wafer.     

推力瓦热瞬态变形机理及抑制方法研究

针对核主泵水润滑推力轴承在事故工况下的热瞬态过程,建立了热固耦合瞬态有限元分析模型。基于所建立模型,分析了常见两层和三层结构推力瓦热瞬态过程瓦面变形,重点分析了三层结构推力瓦隔热层厚度对瓦面变形的影响。随后,进一步探索了遏制瓦面凹变形的方法,阐明了热瞬态过程中瓦面温度场分布不均是产生瓦面凹变形的主因。进一步提出一种新型包边式推力瓦,并仿真验证其能够有效降低热瞬态过程瓦面凹变形,为核主泵水润滑推力轴承的推力瓦设计提供了新思路。