应力偶流体润滑轴承油膜压力和轴心轨迹计算

根据应力偶流体动态润滑轴承雷诺方程,运用数值计算方法研究应力偶参数对轴承润滑性能的影响。针对某柴油机轴承,分别计算采用牛顿流体和非牛顿应力偶流体润滑时的油膜压力分布和轴心轨迹。结果表明：与牛顿流体润滑相比,应力偶流体润滑时轴承的油膜压力增加,且随应力偶参数的增加,最大油膜压力出现在轴承角度增大的方向;2种润滑条件下,所计算得到的轴心轨迹形状类似,不同之处在于牛顿流体润滑时其轴心轨迹离轴承的中心比较远,而应力偶流体润滑条件下轴心轨迹随参数增加向其中心靠近且最小油膜厚度明显增大。研究表明,应力偶流体润滑与牛顿流体相比提高了油膜压力,改善了轴心轨迹,且应力偶参数越大应力偶效应越显著。     

考虑应力偶效应的非牛顿磁流体轴承润滑性能分析

基于考虑应力偶和磁场的雷诺方程,对非牛顿磁流体润滑轴承进行数值分析。研究了不同应力偶参数、磁力系数对液膜压力、承载力以及偏位角的影响,并与牛顿流体数值结果进行比较。结果表明,相比于牛顿流体润滑剂,应力偶效应将显著改善轴承润滑性能,随着应力偶参数的增大,压力和承载力随之增大,且偏心率较大时,压力和承载力随应力偶参数的变化幅度明显;随着磁力系数的增大,压力和承载力相应增大,偏位角减小,且应力偶参数越大,磁力系数对压力、承载力及偏位角的影响越显著,同时液膜破裂初始点右移,空穴区域缩小。     

基于质量守恒边界条件的应力偶流体润滑动载轴承特性

基于应力偶流体理论和改进的Elrod空穴算法对动载轴承的润滑性能进行数值摸拟.求解质量守恒边界条件的动载Reynolds方程,结果表明:与Reynolds边界条件下的结果相比,采用质量守恒边界条件得到的平均进油流量与平均端泄流量更加接近,更符合实际情况.数值求解基于质量守恒边界条件下,应力偶流体润滑的动载Reynolds方程,比较牛顿流体和应力偶流体对轴承的最大油膜压力、最小油膜厚度和端泄流量的不同影响.结果表明:应力偶流体使得动载轴承的最大油膜压力减小,最小油膜厚度明显增大,端泄流量减小,提高了动载轴承的承载能力.     

考虑应力偶计入区间及黏压效应的倾斜轴承非牛顿流体润滑特性研究

以滑动轴承为研究对象,考虑轴颈倾斜及润滑油黏压效应影响,建立轴承应力偶流体动力润滑模型,引入临界油膜厚度系数,探究应力偶流体对油膜厚度的敏感度,分析应力偶流体计入区域、应力偶系数、倾斜角及黏压效应对轴承润滑特性的影响.结果 表明:随着应力偶系数的增加,润滑特性参数随油膜厚度的敏感度逐渐增加.较牛顿流体,考虑滑油应力偶效应时,轴承油膜压力显著增加,且随着应力偶计入区域的增加,轴承最大油膜压力逐渐增加,摩擦因数逐渐减小.在最小油膜厚度区域附近计入应力偶效应时,影响最为显著.轴颈发生倾斜时,倾斜作用将加剧应力偶效应,且随着应力偶系数的增加,倾斜对应力偶效应的影响愈加显著.黏压效应对应力偶流体轴承油膜压力有显著影响,但对于摩擦因数及端泄流量,其影响微弱.     

船舶可倾瓦推力轴承工况参数对润滑特性的影响

为研究船舶工况参数对可倾瓦推力轴承稳态和瞬态润滑特性的影响,利用Matlab建立船舶可倾瓦推力轴承热弹流体动压润滑计算模型,考虑轴瓦的热弹性变形,联立黏温方程、能量方程、油膜刚度和阻尼系数方程求解模型,研究热弹性变形以及不同载荷和转速情况下船舶可倾瓦推力轴承的润滑特性。结果表明：考虑热弹性变形时,最小油膜厚度增大,最大油膜压力和最高油膜温度降低;在正常运行工况条件下,轴瓦的热弹性变形有利于改善推力轴承的润滑性能,轴承设计时应考虑材料的抗压性和耐热性;在转速不变时随着载荷的增大,最小油膜厚度降低,最大油膜压力、温度、油膜刚度和阻尼均增加,需要特别注意重载工况下轴承的动压润滑状况;在载荷相同的情况下,随着转速的提高,油膜厚度和油膜温度增大,油膜压力变化不明显,油膜刚度和阻尼随转速增大而降低,在转速较低时下降较为明显。研究结果为优化轴承设计、提高轴承运行的可靠性和稳定性提供参考。     

PM流量控制器节流液体静压轴承静动态特性分析

将PM流量控制器用于无周向回油槽四腔向心静压轴承,建立了PM流量控制器静压轴承数学模型,重点研究分析了轴承结构参数及PM流量控制器参数对静压轴承特性的影响。研究结果表明:轴承轴流封油边系数越小、周流封油边系数越大,轴承油膜刚度和承载力越大,初始油膜间隙增大,油膜刚度减小;润滑油动力粘度较大且初始油膜间隙较小时,油膜刚度和承载力较大;液阻比越小,比流量越大,油膜刚度越大;供油压力越大,油膜刚度、承载力和流量越大。同时基于线性化下液体静压轴承系统的传递函数,利用Matlab Simulink软件在时域和频域内分别研究了静压轴承系统的动态特性。研究结果表明:在阶跃载荷作用下,随着供油压力和比流量的提高,过渡过程时间越短,静压轴承系统的动态特性越好;在正弦载荷作用下,提高供油压力、比流量都会使轴心偏移量的稳态幅值减小,油膜动刚度增大,且供油压力较比流量对系统频率特性的影响显著。     

气穴对涡轮增压器浮环轴承油膜力的影响

气穴是高速油膜润滑轴承中不可避免的现象,气穴现象影响浮环轴承油膜承载力及稳定性。通过Fluent 软件中的混合物（Mixture）多相流模型,分析气穴对浮环轴承内、外油膜压力分布以及含气率和供油压力对油膜承载力的影响。结果表明：气穴导致油膜压力峰值下降,对内油膜的影响大于外油膜;气穴会导致润滑油膜承载力下降,含气率越大,其承载力越低;在含气率不变时,供油压力对承载力有一定影响;油膜气穴主要集中分布在负压区,油膜压力值越小气穴现象越明显,气穴是导致油膜破裂的主要原因之一。     

斜面推力滑动轴承承载性能研究

随着机械设备日益重载化、高速化,给滑动轴承承载性能提出更高要求。通过使用FLUENT软件,构建轴承油膜润滑模型,并选定适合的参数进行计算,主要探究油膜厚度、油槽位置以及瓦块倾角不同时滑动轴承承载力的变化情况,找出内在规律。研究结果显示,油膜越小,轴承承载力越大;膜厚固定时,随着轴瓦倾角的增大,轴承承载力会先增大后减小;油槽位置外移程度越大,则轴承承载力提升越明显。     

内燃机主轴承EHD模拟计算研究

在充分考虑轴承座、瓦背、减摩合金层的弹性变形及轴颈、轴瓦表面粗糙度因素的影响基础上,对某4100QB柴油机主轴承进行了综合的EHD模拟计算研究。采用有限差分法与有限元法相结合对轴承的油膜压力、油膜厚度、弹性变形、表面粗糙度进行了耦合分析,并将EHD耦合算法结果与刚性分析结果及仅考虑轴瓦弹性变形的分析结果进行了比较分析。结果表明,综合考虑轴承座、瓦背、减摩合金层弹性变形及轴颈、轴瓦表面粗糙度因素影响的弹流润滑研究更符合实际工况,其油膜厚度增大,油膜压力减小,油膜承载区扩大,且在轴承载荷峰值处表现最为明显。     

轴颈转速对滑动轴承油膜特性及轴瓦结构特性的影响

为了更加精确地分析高转速下内燃机轴承轴瓦的受力情况,明确不同轴颈转速对轴瓦的受力规律的影响,采用流-固顺序耦合的方法,在滑动轴承油膜的CFD分析模型的基础上,建立轴瓦的有限元分析模型,并基于该模型得到不同轴颈转速下油膜压力、承载力、油膜组分分布以及轴瓦应力、应变随轴颈转速的变化规律。研究结果表明：随着轴颈转速的增加,油膜的压力不断增大,轴瓦载荷不断增加,轴瓦应力、变形逐渐增大;油膜最大压强随轴颈转速的增加几乎呈线性增长,导致轴瓦的最大应力值及最大变形也几乎呈线性增大;随着轴颈转速的增加,润滑油入口附近,润滑油体积分数逐渐减小,油膜破碎区内,润滑油体积分数的梯度更加明显。     

Coupled couple stress and surface roughness effects on elasto‐hydrodynamic contact

This paper deals with the combined effects of couple stress and surface roughness to inspect the elasto‐hydrodynamic performance of slider bearing systems. On the basis of the couple stress Stokes theory and homogenisation method, the homogenised generalised Reynolds equation including the slider bearing stationary surface deformation is derived. The total deformation include the deformation of smooth surface, taken into account by the elastic thin layer model, and the deformation of roughness corresponding to a sinusoidal normal displacement on an elastic half space of identical wavelength. The governing equations are discretised by the finite difference method, and the obtained algebraic equations are solved using the iterative overrelaxation Gauss–Seidel technique. The load‐carrying capacity and friction coefficient are presented for transverse, longitudinal and anisotropic roughness patterns for different values of the couple stress parameter in both rigid and deformable cases. The simulation results indicate that the interaction between couple stress, surface roughness and elastic deformation effects is significant. Copyright © 2013 John Wiley & Sons, Ltd.     

The Static and Dynamic Characteristics of a Two-Lobe Journal Bearing Lubricated with Couple-Stress Fluid

Static and dynamic characteristics of two-lobe journal bearings lubricated with couple-stress fluids are studied. The load-carrying capacity, the stiffness and damping coefficients, the non-dimensional critical mass, and the whirl ratio are determined for various values of the couple stress parameter l. The results obtained are compared with the characteristics of two-lobe bearings lubricated with Newtonian fluids. It is found that the effect of the couple stress parameter is very significant on the performance of the journal bearing. The stability is improved compared to bearings lubricated with Newtonian fluids.     

The effects of surface irregularities on the performance characteristics of flexible finite journal bearings lubricated with couple stress fluids

A numerical solution for the elastohydrodynamic lubrication of finite journal bearings is presented. Couple stress effects resulting from blending the lubricant with various additives are considered. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearings, is implemented in the solution scheme. A simple elastic model is used to describe the elastic deformation of the bearing liner. Furthermore, the effects of surface waviness on the performance of the bearing are incorporated into the analysis. A comprehensive study illustrates the effects of couple stress, liner flexibility, and surface waviness on the steady‐state performance of finite‐width journal bearings. The results show that these effects should be considered at higher values of the eccentricity ratio.     

Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 1: Experiment and theory

In this paper, the load-carrying capacity, power losses and stiffness of disk-type hydrostatic thrust bearings including the case of eccentric loading are discussed theoretically. The numerical analysis method is established based on a two-dimensional elastohydrostatic problem with an elastic deformation model, which is extended to adapt it for a non-axisymmetric load acting on the thrust bearing. The bearing is made of a combination of stainless steel/stainless steel and stainless steel/plastics. For the elastic materials, the maximum stiffness derived from, i.e., minimum film thickness is, larger than that of the rigid material in the range of a large ratio of pocket pressure and a hydrostatic balance ratio of over unity, which is defined as the ratio of the load to the maximum hydrostatic load-carrying capacity. The maximum load-carrying capacity and minimum power loss can exist in the domain of the hydrostatic balance ratio over unity for the case of the bearing consisting of elastic/rigid materials, in comparison with that composed of the same rigid materials. For the case of water, the power loss due to leakage flow is slightly larger but that due to frictional torque is much smaller than that in the case of hydraulic oil. Then, the total power loss is much smaller than that of hydraulic oil.     

Investigations on the Influence of Surface Texturing on a Couple Stress Fluid–Based Journal Bearing by Using JFO Boundary Conditions

The present study was conducted to examine the effect of laser surface texturing combined with couple stress fluids on the hydrodynamic lubrication of finite journal bearing in this work. The Jakobsson-Floberg-Olsson (JFO) boundary conditions were engaged instead of Reynolds boundary conditions to achieve realistic results. Moreover, the results were computed and authenticated with the previous published work. It was observed that the load-carrying capacity is increased with couple stresses for smooth journal bearings at different eccentricity ratios. However, the increment in load-carrying capacity with texture affects only at low eccentricity ratios. The combined effects of texturing with couple stress fluids lower the performance of journal bearings at different eccentricity ratios.     

Approximate Solution of Oil Film Load-carrying Capacity of Turbulent Journal Bearing with Couple Stress Flow

The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.     

Static Performance of Finite Hydrodynamic Journal Bearings Lubricated by Magnetic Fluids with Couple Stresses

Based upon the Stokes micro-continuum theory, the problem of lubrication of finite hydrodynamic journal bearing lubricated by magnetic fluids with couple stresses is investigated. By taking into account the couple stresses due to the microstructure additives and the magnetic effects due to the magnetization of the magnetic fluid, modified Reynolds equation is obtained. The effects of couple stresses are studied by defining the couple stress parameter L that can be considered as a measure of the chain length of the additive molecule. The magnetic effects of the magnetic fluid are investigated by the magnetic coefficient γ. Using the finite-difference technique and for different values of couple stress parameter and magnetic coefficient, the Reynolds equation is solved, and pressure distributions are obtained. The bearing static characteristics namely load carrying capacity, attitude angle, friction coefficient, and side leakage flow are determined. The results indicate that the influence of couple stresses and magnetic effects on the bearing characteristics are significantly apparent. It is concluded that fluids with couple stresses are better than Newtonian fluids. The improvement of the bearing characteristics is enhanced if the magnetic effects are present.     

Misalignment effects on steady‐state and dynamic behaviour of compliant journal bearings lubricated with couple stress fluids

This work concerns the steady‐state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro‐continuum theory, a modified form of the Reynolds equation is derived. The displacement field at the fluid film–bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load‐carrying capacity, power loss, side leakage flow, misalignment moment, critical mass and whirl frequency are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Lubrication performance of finite journal bearings considering effects of couple stresses and surface roughness

To inspect the performance characteristics of finite journal-bearing systems, the combined effects of couple stress due to a Newtonian lubricant blended with additives and the presence of roughness on journal-bearing surfaces are studied in this article. Basing on the Stokes theory and Christensen’s stochastic model, the stochastic generalized Reynolds equation is deduced. The film pressure distribution equation is numerically solved by using the conjugate gradient method of iterations. According to the results, the couple stress effects can raise the film pressure of the lubricant fluid, improve the load-carrying capacity and reduce the friction parameter, especially at high eccentricity ratio. The surface roughness effect is dominant in long bearing approximation and the influence of transverse or longitudinal roughness to the journal bearing is in reverse trend. In general, the critical value of length-to-diameter is 1.1.     

Modified Reynolds Equation for Different Types of Finite Plates with the Combined Effect of MHD and Couple Stresses

We make an effort to analyze the behavior of squeeze film characteristics of different finite plates with couple stress fluid in the presence of a transverse magnetic field. On the basis of the Stokes couple stress fluid model and hydromagnetic flow model, a modified Reynold's equation is derived, which is solved by using appropriate boundary conditions to obtain squeeze film pressure, load-carrying capacity, and squeeze film time. The graphical representation of the results suggests that the different bearing systems register an enhanced performance with couple stresses compared to that of a bearing system working with a conventional lubricant in the presence of a transverse magnetic field. It is observed that the effect of applied magnetic field on the squeeze film lubrication between different finite plates with conducting couple stress fluids is to increase the load-carrying capacity significantly and to delay the time of approach compared to the corresponding nonconducting Newtonian case. It is seen that for all of the finite plates of different shapes, the circular shape gives the maximum load and time.