表面织构排布方式对径向滑动轴承摩擦性能的影响

基于Navier-Stokes方程,建立表面织构化滑动轴承数值分析模型,采用压力耦合方程的改进半隐式(SIMPLEC)算法进行求解,分析表面织构排布和形状对滑动轴承摩擦性能的影响。结果表明：在收敛楔入口排布十字形织构时可以显著提高承载能力;在收敛楔中部周向排布沟槽和短沟槽织构比轴向排布更能显著改善轴承摩擦性能,且排布倒椭圆、菱形和十字纹理可以更明显地改善滑动轴承的摩擦性能;在收敛楔出口排布织构不能改善滑动轴承的摩擦性能,而在发散楔只有三角形织构可以改善轴承的摩擦性能。设计5种新型复合织构排布方式,分析其对轴承摩擦性能的提升效果。结果发现：复合型织构比单一类型织构更有利于提高轴承摩擦性能,其中在收敛楔入口布置十字形织构,收敛楔中部分别布置周向沟槽、短沟槽和十字形织构,发散楔布置三角形织构的3种复合型织构设计轴承性能提升效果显著,使承载力分别提高了15.69%、15.66%和17.16%,摩擦因数降低了3.75%、4.17%和2.92%。     

表面织构动压滑动轴承油膜力解析模型

提出一种求解表面织构动压轴承油膜力的解析模型。基于Sommerfeld油膜边界,通过分离变量的方法,求解表面织构动压滑动轴承二阶偏微分Reynolds方程,得到表面织构动压滑动轴承油膜压力解析式。以圆形凹坑轴承为例,在油膜区域通过积分求得织构轴承的油膜力,分析织构参数对油膜压力的影响,研究发现,表面织构位于收敛区域(升压区)的轴承,其润滑与承载性能优于表面织构位于发散区域(降压区)的轴承、全织构轴承以及光滑轴承。对比了提出的解析模型与FDM和CFD模型在不同长径比和偏心率下的计算结果,结果表明,提出的解析模型能准确地描述表面织构动压滑动轴承的油膜力,且计算结果同FDM和CFD模型计算结果基本一致,验证了该模型的正确性。     

界面滑移对圆柱形凹坑织构滑动轴承摩擦力的影响

为研究不同的滑移情况对圆柱形凹坑织构滑动轴承摩擦力的影响,建立含有圆柱形凹坑织构的滑动轴承在不同界面滑移状态下的摩擦力计算模型,探究影响织构化滑动轴承摩擦力的参数,并借助ANSYS分析不同滑移情况下界面滑移对圆柱形凹坑织构滑动轴承摩擦力的影响规律。结果表明:织构化滑动轴承的摩擦力主要是由轴颈线速度、油膜滑移比、轴承的进出油口压力、织构处油膜压力、织构深度、油膜厚度和承载力决定;不同滑移情况下织构模型的摩擦力均小于无织构模型;且在上下表面均滑移时,圆柱形凹坑织构在出口位置时表现出最优的承载和减摩效果;适当地增加圆柱形凹坑织构的深度可以改善模型的摩擦性能,但是过深的凹坑织构并不能发挥出其性能。     

Effect of textured area on the performances of a hydrodynamic journal bearing

A growing interest is given to the textured hydrodynamic lubricated contacts. The use of textured surfaces with different shapes of microcavities (textures) and at different locations of the texture zone can be an effective approach to improve the performance of bearings. The present study examines the texture location influence on the hydrodynamic journal bearing performance. A numerical modelling is used to analyze the cylindrical texture shape effect on the characteristics of a hydrodynamic journal bearing. The theoretical results show that the most important characteristics can be improved through an appropriate arrangement of the textured area on the contact surface.     

卧式水电机组局部多油楔径向滑动轴承研究

针对卧式水电机组用径向滑动轴承载荷日益提高的现状,设计一种局部多油楔瓦面结构的径向滑动轴承。通过联立求解膜厚方程、雷诺方程、密度方程、黏度方程、能量方程和固体热传导方程等,获得轴承的热流润滑特性,并与椭圆径向滑动轴承的热流特性进行对比。结果表明,局部多油楔径向滑动轴承具有较大的动压承载区域和较小的油膜压力梯度以及较低的油膜温升,可以大幅度提高轴承的承载能力。     

精密多油楔动压轴系的楔形间隙参数与油膜运动稳定特性

针对精密仪器轴系的研制和精度分析,研究了立式三油楔动压轴系的结构、轴承轮廓结构,建立数学模型、分析模型,对轴系动压油膜的动力特性做了分析.对于主轴在动压油膜反力与外载荷作用下处于某一平衡位置(e,θb)运转时,能否经得起任意微扰动的干扰而失稳,建立了油膜运动稳定性的判据.应用数值模拟和计算机编程,深入研究了关键设计参数楔形间隙bm、cm相应的油膜运动稳定特性,揭示了楔形间隙值与轴系失稳的对应关系,给出了油膜稳定性因数Log(Sp)与偏心率ε(ε=e/c)之间的变化曲线图,并指出了楔形间隙参数最佳的取值范围.研究结果指出:楔形间隙是轴系设计和制造的重要敏感参数;最大楔形间隙bm和最小间隙cm值之间应保持一定的比例,否则油膜运动发散,轴系平衡失稳,导致主轴转动中产生较大的晃动.对于低速立式三油楔动压轴系,则bm-cm≥0.8 μm.比较研究结果与成功轴系实例,表明实例中bm、cm取得符合轴系的油膜稳定条件.证明研究结果对该类轴系的设计具有实用性.     

非对称结构表面织构对滑动轴承摩擦性能的影响

为揭示织构凹坑方式对径向滑动轴承摩擦性能的影响,基于气液两相流理论,建立径向滑动轴承腔内油气两相流数值计算模型.将传统普通织构改进为出入口呈阶梯状的非对称织构,定义出入口壁面高度比值H为非对称因数,采用SIMPLEC算法进行求解,分析非对称因数对凹槽织构单元流体域内流场的影响,探讨径向滑动轴承不同位置织构、不同转速下非...     

Hybrid journal bearings with particular reference to hole-entry configurations

There is a spectrum of pressure-fed journal bearings ranging from the purely hydrostatic bearing characteristics, ie zero speed operation, to the purely hydrodynamic bearing characteristics which depend completely on speed. Between these two extremes, hybrid bearing characteristics rely on mixed modes of external pressurisation and speed-dependent pressurisation. Large high speed hydrodynamic bearings require the lubricant to be pumped under pressure for temperature control. It is therefore attractive to use this external source of pressure to enhance the start-up performance by reducing wear and improving stability. Hybrid bearings offer the possibility of improving on both the zero-speed characteristics of hydrostatic bearings and on the whole range of speed characteristics of hydrodynamic bearings. It is concluded that hole-entry bearings may be particularly effective when compared with other bearing configurations for good load support and low energy consumption, when used in any of the four modes of operation including: zero-speed hydrostatic mode; high-speed hydrodynamic mode; zero and high-speed hybrid mode; and jacking mode where areas are pressurised for start-up. A modification to the procedure for solving the Reynolds equation is introduced to cope with cavitated regions. The technique presented for solving the bearing pressures and cavitation boundaries is efficient and has relevance to any type of liquid film bearing     

Squeeze films in full porous metal bearings

The behaviour of squeeze films in porous journal bearings under a steady load is analysed. A full journal bearing with a non-rotating journal is considered. The Reynolds equation governing the pressure in the film region is modified to take account of the mass exchange of the lubricant between the film and the bearing matrix. In the case of thin-walled bearing (H?R), the modified Reynolds equation takes a simpler form. However, since this equation cannot be solved directly as applied to a finite bearing, solutions in a closed form are found both for the long bearing and narrow bearing approximations. It is found that the permeability of the bearing matrix and the wall thickness of the bearing adversely affect the load capacity and greatly reduce the time needed for the journal to attain a given eccentricity. With a permeable bearing, there is the possibility of the journal coming into contact with the bearing (ε=l) in a finite time. Generally the performance of a long bearing is better than that of a narrow bearing.     

Feasibility Study of Hydrodynamic Lubrication in Supporting of Rotating Elements of Galvanizing Hardware Submerged in Molten Zinc

Severe wear of sink roll supports in continuous galvanizing lines has been a cause for concern for some years. This wear, which affects the quality of the coating and downtime costs, is a result of a corrosive environment and highly loaded surface contact.

This paper presents results from a feasibility study to use journal bearings lubricated with molten zinc to separate the interacting surfaces. Analytical and experimental investigations were aimed at identifying the load capacity of sink roll bearings when operating in the hydrodynamic regime, as well as the effect of the molten zinc bath environment on bearing performance. This environment includes chemical zinc attack and the presence of inter-metallic particles in the bath.

The study indicates that it is difficult to achieve hydrodynamic bearing operation for the entire range of operating conditions. It also shows that, when selecting materials for journal bearings support to the rotating elements submerged in molten zinc baths, possible contact of the bearing surfaces as well as chemical inertness and resistance to the hard intermetallic particles do need to be addressed.     

Steady state and stability characteristics of a hydrodynamic journal bearing with a non-Newtonian lubricant

The effect of the non-Newtonian behaviour of lubricants, resulting from the addition of polymers, on the performance of hydrodynamic journal bearings was investigated. An empirical fluid flow equation which adequately represents the flow behaviour of lubricant was used to obtain a modified form of Reynolds' equation. Finite difference numerical solutions were obtained for steady state conditions at various width-to-diameter ratios. The results show a strong influence of the width-to-diameter ratio on the load capacity of journal bearings. Linearised stiffness and damping coefficients were evaluated from the fluid film force equations for the unsteady motion of the journal centre and were used to predict the stability limits of a simple rigid rotor-bearing system which showed a reduction in threshold speeds. The steady state load capacity and stability limits were verified experimentally for finite width bearings.     

Load Capacity Estimation of Foil Air Journal Bearings for Oil-Free Turbomachinery Applications

This paper introduces a simple “Rule of Thumb” (ROT) method to estimate the load capacity of foil air journal bearings, which are self-acting compliant-surface hydrodynamic bearings being considered for Oil-Free turbomachinery applications such as gas turbine engines. The ROT is based on first principles and data available in the literature and it relates bearing load capacity to the bearing size and speed through an empirically based load capacity coefficient, D. It is shown that load capacity is a linear function of bearing surface velocity and bearing projected area. Furthermore, it was found that the load capacity coefficient, D, is related to the design features of the bearing compliant members and operating conditions (speed and ambient temperature). Early bearing designs with basic or “first generation” compliant support elements have relatively low load capacity. More advanced bearings, in which the compliance of the support structure is tailored, have load capacities up to five times those of simpler designs. The ROT enables simplified load capacity estimation for foil air journal bearings and can guide development of new Oil-Free turbomachinery systems.     

Floating ring journal bearings: theory, design and optimization

The performance characteristics and design data for journal bearings with a precise floating ring inserted between the rotating journal and a rigid housing are investigated theoretically. Based on convenient boundary conditions, a theory has been developed to predict the floating ring behaviour. Performance charts are presented with curves provided with optimum design areas to help in practical design applications. Induced ring speed, hydrodynamic behaviour, oil film variation, load capacity and frictional drag could thus be analytically or graphically determined. Results indicate that the ring dimensions are a dominant factor in deciding the final bearing behaviour and that the oil film thickness between the ring and the housing is much thinner than that between the journal and the ring. The floating ring bearing showed less frictional power loss than a fixed sleeve bearing, but this may have been achieved at the expense of the load capacity.     

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。     

考虑不同加速工况的滑动轴承的启停性能分析*

滑动轴承的摩擦磨损主要发生在启停阶段。为了研究启停工况下的滑动轴承的摩擦学性能,建立一种面向径向滑动轴承的混合润滑数值分析模型。采用质量守恒边界条件的雷诺方程求解流体压力,采用Greenwood和Tripp接触模型预测固体表面接触,而通过Johnson载荷分配概念将润滑模型和接触模型联系起来,从而实现对滑动轴承在启停工况下从混合润滑过渡到动压润滑的摩擦学行为分析。利用该模型,研究轴承系统在启停阶段从边界润滑、混合润滑到动压润滑演化过程中的摩擦学性能;以径向滑动轴承系统为例,结合不同的轴承转速变化函数,分析轴承加速对轴承启停性能的影响;同时研究工作工况、润滑油温度、轴承的结构参数对轴承启停性能的影响。结果表明：轴承启动加速度在合理范围内越大越好,能使轴承更快进入动压润滑;较高的转速、较低的润滑油温度和较大的径向轴承间隙能使轴承拥有更好的启停性能。     

UHMWPE基水润滑尾轴承润滑特性仿真及试验研究

针对UHMWPE基高分子复合材料水润滑轴承的润滑特性开展研究。采用双向流固耦合算法研究弹性模量和泊松比等材料参数以及转速、负载等工况参数对水润滑轴承偏心率、最大水膜压力、轴承最大变形量、最小水膜厚度、摩擦因数等润滑特性的影响。基于改性UHMWPE高分子复合材料轴承的试验,验证了仿真方法的正确性。研究表明:计入弹性变形的流固耦合算法在研究高分子复合材料轴承性能方面具有更高的精度;随轴瓦材料弹性模量和泊松比的增大,轴承承载力逐渐增大、弹性变形量逐渐减小;随负载增大,轴承最大水膜压力和最大变形量基本呈线性增长;随转速增大,轴承最大水膜压力和轴承最大变形量显著减小;对于高分子复合材料轴承,低速、重载工况下不计入弹性变形的算法误差更大。     

评价箔片径向空气轴承载荷性能的一种经验方法

介绍一种简单的“经验法则”来评价箔片空气轴承的载荷性能,它是一种可挠面的动压气体轴承,正在研究其在无油透平机械中的应用。经验法则是基于基本原理和文献中报道的可靠实验数据得出的,通过一个经验值——载荷系数D,将轴承的载荷性能和轴承的尺寸、速度联系起来。在经验法则中,轴承承载力是轴承转速和轴承设计面积的线性函数。轴承载荷系数D和轴承弹性支承结构的设计特点和轴承运行工况(温度、速度)有关。     

Calculation of oil‐film thickness in journal bearings running at varying rotational speeds

There are many methods of calculating the properties of lubricated hydrodynamic sliding bearings running at variable loads, but, in some cases, sliding bearings of heavy‐duty machines run under constant load and at variable speeds; this can lead to reduced film thickness in the bearing and boundary lubrication. The minimum oilfilm thickness in such a bearing needs to be calculated so that the proper lubricant viscosity can be selected to reduce solid‐solid contact during machine operation. In this study, a method is presented for calculating the film thickness of sliding bearings operating with alternating rotational directions. The results of the calculations show that the squeeze effect can develop enough load‐carrying capacity to prevent solid‐solid contact between the rubbing surfaces during operation, provided the change of direction of rotation is quick enough.     

Influence of lubricants on the performance of journal bearings – a review

ABSTRACT

The lubricant properties have a significant influence on the static and dynamic performance characteristics of journal bearing such as load-carrying capability, minimum fluid film thickness, maximum pressure, lubricant flow rate, damping coefficients, stiffness coefficients, etc. The present document reviews the behaviour of various lubricants such as power-law lubricants, couple stress lubricants, micropolar lubricants, ionic liquid lubricants and space lubricants. The influence of these lubricants on the performance of hydrostatic, hydrodynamic and hybrid journal bearings is discussed. An effort is made to develop the understanding to choose the suitable lubricant for journal bearings for different journal bearing configurations. Journal bearings operated with non-Newtonian lubricants have shown better performance compared to Newtonian lubricants. Ionic liquid lubricants have shown high potential in vacuum applications and extreme temperature environment such as in bearings of spacecraft moving mechanical assemblies.     

考虑粗糙度的船舶水润滑高分子轴承弹流润滑性能研究

为了揭示表面粗糙度对船舶水润滑高分子材料轴承润滑性能的影响规律,开展水润滑轴承弹流混合润滑理论研究;建立考虑内衬材料粗糙度和弹性变形的水润滑轴承混合润滑模型,并对模型进行仿真验证;分析内衬粗糙峰对水膜厚度、水膜压力分布和承载能力的影响规律。研究结果表明：在转速增大的过程中,内衬粗糙度的增大会减缓水膜厚度的增幅比,使轴承需要更高的转速来进入流体动压润滑状态;减小轴承内衬粗糙度能有效降低轴承起飞转速,加快轴承由混合润滑转变为流体动压润滑的过程,减小轴承与轴颈的局部接触,降低轴承异常振动噪声发生的可能性。研究结果揭示了内衬粗糙度变化对轴承润滑特性的影响机制,为水润滑轴承的优化设计提供理论参考。