计入轴瓦弹性的应力偶流体润滑分析

推导了计入轴瓦弹性的应力偶流体润滑轴承的变形雷诺方程。数值分析表明,刚性轴瓦的最大油膜压力值比弹性轴瓦的最大油膜压力值大,且随着应力偶参数的增大,最大油膜压力提高明显;润滑油分别为牛顿流体和应力偶流体时,弹性系数越大轴承的承载力越小,应力偶参数越大轴承的承载力越大,且轴承的偏心率越大,应力偶参数对承载力的影响越明显,应力偶参数对刚性轴瓦材料的影响比对弹性轴瓦材料的影响大。     

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.     

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。     

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。     

圆柱滚子轴承的微观非牛顿热弹流润滑分析

为研究滚动轴承中接触副间的弹流润滑性能,基于滚动轴承,建立圆柱滚子与轴承外圈接触的微观非牛顿热弹流润滑模型,分析牛顿流体和非牛顿流体在不同特征剪应力、滑滚比、载荷参数条件下的差异,并考察不同粗糙度幅值及波长的影响。结果表明,滚子端部温度受特征剪应力的影响比滚子中部大,在粗糙度的影响下,油膜温度波动幅度随特征剪应力的增大而增大;牛顿流体和非牛顿流体油膜温度及摩擦因数均随着滑滚比、载荷的增大而增大,且牛顿流体油膜温升和摩擦因数明显大于非牛顿流体;接触区内的油膜厚度、压力及温度的波动随着粗糙度幅值的增加波动越剧烈,而随着粗糙度波长的增加波动趋于平缓,并且由于粗糙度的影响,在滚子中部产生的局部温升随滑滚比、载荷的增大而增大。     

基于多体动力学的船用柴油机连杆轴承润滑分析

基于多体动力学有关理论,计入影响滑动轴承弹流动压润滑的有关因素,构建连杆轴承仿真计算模型,采用有限元法对二冲程船用柴油机额定工况下的连杆大端和小端轴承的润滑状况进行研究。根据在一个工作循环内的计算结果可以发现:小端轴承即十字头轴承始终承受压应力,而大端轴承短时间内存在拉应力,垂向载荷方向改变;载荷的最大值皆发生在缸内气体压力最大的时刻;小端轴承高油压区域十分集中,其轴心运动轨迹存在于下半部较小的范围内;大端轴承轴心轨迹主要存在于上半部的右半部分; 2个轴承的平均油膜压力分布皆较为集中;连杆两轴承的油膜最小厚度皆大于3μm,能满足流体动压润滑的要求。     

柴油机主轴承弹性流体动力学与多体动力学耦合仿真

为更准确分析柴油机主轴承润滑特性及其影响因素,根据动载滑动轴承弹性流体动力润滑模型,利用AVLExcite软件对4D32柴油机主轴承进行多体动力学与弹性流体动力学耦合仿真研究。探讨了各主轴承载荷、最小油膜厚度、轴心轨迹、摩擦损失功率、机油填充率等参数在一个工作循环内的变化规律,并对比了主轴承最小油膜厚度随油槽方向和油孔位置等因素的变化关系。结果表明,最小油膜厚度的极小值均大于2μm,对其进行计算时要考虑边界接触压力的影响;第3主轴承轴心轨迹曲线绝大部分落在最外端,偏心率最大值持续期较长,最大油膜压力时间交替作用在轴瓦表面,极易引起轴瓦的磨损和疲劳剥落;优化设计油槽、油孔的方向和位置,有利于流体动压润滑的形成。     

油水两相流对轧机油膜轴承热弹流润滑的影响

研究润滑油中混入水后对轧机油膜轴承热弹流润滑的影响。建立油水两相流体的数学模型,以及轧机油膜轴承热弹流润滑的数学方程,利用多重网格法及多重网格积分法对上述方程进行求解,并分析润滑膜压力、膜厚随含水量、主轴转速、轧制力的变化关系。结果表明:与纯油润滑相比,油水两相流体润滑具有更好的润滑特性,且随着含水量的增加,膜厚增大,承载能力增强;随着主轴转速的增加,膜厚增加,承载能力减小;随着轧制力的增加,膜厚减小,承载能力增强。在油水两相流润滑条件下,热效应对于轧机油膜轴承弹流润滑的影响不能忽略。     

计入曲轴受载变形的粗糙表面曲轴轴承弹性流体动力润滑分析

对一四缸内燃机曲轴轴承进行了计入曲轴受载变形和表面形貌的弹性流体动力润滑分析.计算中采用动力学法进行曲轴轴承的润滑分析,采用变形矩阵法计算油膜压力作用下轴瓦表面的变形.结果表明,表面形貌对曲轴轴承轴心轨迹影响较大,表面弹性变形对曲轴轴承轴心轨迹影响很小;计入表面形貌,曲轴轴承最大油膜压力增大显著,最小油膜厚度明显减小,端泄流量在大部分时间几乎没有变化;计入表面弹性变形,轴承最大油膜压力基本都有不同程度的减小;表面弹性变形对端泄流量、轴颈摩擦因数以及最小油膜厚度的影响甚小.     

基于Carreau流变模型的圆柱滚子轴承热混合润滑分析*

为了研究圆柱滚子轴承接触区的混合润滑性能,建立基于Carreau非牛顿流体的热混合润滑模型,求解非牛顿流体线接触热混合润滑数值解。研究滑滚比、卷吸速度及载荷对线接触混合润滑特性的影响,并与相同工况下牛顿流体热混合润滑的结果进行对比。结果表明：随着滑滚比、卷吸速度及载荷的增大,油膜温度都会升高,Carreau非牛顿流体的温度要低于牛顿流体的温度;油膜厚度随着滑滚比、载荷的增大而减小,随着卷吸速度的增大而增大,Carreau非牛顿流体与牛顿流体膜厚相差不大;随着滑滚比的增大,2种流体的平均摩擦因数均增大,随着卷吸速度和载荷的增大,2种流体的载荷比均减小。     

On the performance of dynamically loaded journal bearings lubricated with couple stress fluids

A numerical study of the performance for a dynamically loaded journal bearing lubricated with couple stress fluids is undertaken. First of all, on the basis of micro-continuum theory, the generalized Reynolds equation for dynamic loads is derived. Then it is simultaneously solved with the force balance equation of the journal, thus obtaining the transient oil film pressure, the transient position and velocity of the journal center. Results from this analysis are presented for a typical engine crankshaft bearing. It is shown, compared with Newtonian lubricants, that under a dynamic loading lubricants with couple stress yield an obvious increase in oil film pressure and oil film thickness, but a decrease in the side leakage flow. Moreover, the effects of couple stress on friction force and friction coefficient vary considerably with time.     

The lubrication of lightly loaded cylinders in combined rolling, sliding and normal motion with couple stress fluid

The lubrication of lightly loaded cylinders with combined rolling, sliding and normal motion is investigated with a couple stress fluid as lubricant under cavitation boundary conditions. It is shown that the major bearing performance characteristics can be accounted for by means of a dimensionless parameter, q, involving the “normal” and “entraining” velocities, the minimum film thickness and the radius of the geometrically equivalent cylinder near a plane. The load capacity and frictional drag increase as the squeeze velocity increases. This increase is enhanced by decreasing the couple stress parameter, τ. However, when the two surfaces move apart these results are reversed. It is convenient to adopt the least-squares procedure for the accurate representation of the line of cavitation and the line of maximum pressure. The effect of couple stresses on the point of cavitation is quite significant compared with viscous fluid of the same viscosity.     

Hydrodynamic lubrication of rough slider bearings with couple stress fluids

The combined effects of couple stresses and surface roughness on the performance characteristics of hydrodynamic lubrication of slider bearings with various film shapes, such as plane slider, exponential, secant and hyperbolic, are studied. A stochastic random variable with non-zero mean, variance and skewness is used to mathematically model the surface roughness of the slider bearing’s. The Stokes couple stress fluid model is used to characterize the rheological behavior of the lubricant with polymer additives. The modified expressions for the bearing characteristics, namely pressure, load carrying capacity, center of pressure, frictional force are obtained for the general lubrication film shape on the basis of Stokes microcontinuum theory for couple stress fluids. Results are computed numerically for various film shapes under consideration. It is observed that, for all the lubricant film shapes under consideration, the negatively skewed surface roughness increases the load carrying capacity, frictional force and temperature rise, while it reduces the coefficient of friction. On the contrary, the reverse trend is observed for positively skewed surface roughness. Further, these effects are more pronounced for the couple stress fluids.     

轴承腔中均匀流体/壁面油膜分层流动分析

航空发动机轴承腔精确的润滑与换热设计依赖于对其内油气两相润滑介质流动与换热本质的认识。针对轴承腔内复杂的油气两相润滑介质流动状态,建立轴承腔均匀流体/壁面油膜分层流动分析模型,开展腔内油气两相润滑介质流动特性研究,探讨转子转速和润滑油供油量对均匀流体和壁面油膜两相介质压力、速度以及温度分布的影响。分析模型中,气相介质(含油滴)的等效物理特征参数通过离散油滴和气相介质的组分比例关系确定,各固体壁面与流体介质的对流换热系数根据其各自的传热特性确定。研究结果表明,均匀流体与壁面油膜两相介质的压力随着润滑油供油量的增加而增大,受转子转速的影响较为复杂;均匀流体与壁面油膜两相介质的速度随着转子转速的增高而增大,受润滑油供油量影响较小;均匀流体的温度随着润滑油供油量的增加而减小,受转子转速的影响较小;与均匀流体温度不同,壁面油膜的温度随着转子转速的增加而增大,随着润滑油供油量的增加而减小。建立了轴承腔试验台系统,开展了轴承腔油气两相流动状态下的压力和温度测试,压力和温度试验结果与理论计算结果均具有较好的吻合性,验证了提出的理论分析方法的可靠性。     

利用边界层理论确定弹性金属塑料瓦油膜能量方程的进油温度边界条件

针对推力轴承的基本结构,利用边界层理论确定弹性金属塑料瓦（EMP瓦）油膜能量方程的进油温度边界条件,结合“三峡推力轴承方案”中EMP瓦推力轴承数据,分析考虑热边界层对进油温度影响时,EMP瓦推力轴承润滑性能的变化情况。计算结果表明：考虑热边界层对进油温度的影响时,进油平均温度和最高油膜温度均有所升高,最大压力也有所增加,最小油膜厚度、流量及功耗都有所下降,说明热边界层对推力轴承的润滑性能产生了一定的影响。     

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.     

Squeeze film characteristics of conical bearings with combined effects of piezo-viscous dependency and non-Newtonian couple stresses

In this paper, the analysis of squeeze film characteristics of conical bearings with combined effects of piezo-viscous dependency and couple stress fluid is presented. On the basis of the Stokes microcontinuum theory of couple stress fluid model and Barus experimental research, a modified Reynolds equation is derived, the standard perturbation technique is used to solve the highly non-linear Reynolds equation and approximate analytical solution is obtained for the squeeze film pressure, load carrying capacity and squeeze film time. According to the results obtained, the effect of viscosity pressure dependency on the squeeze film lubrication of conical bearings with couple stress fluids is to improve the load carrying capacity significantly and lengthen the squeeze film time as compared to iso-viscous Newtonian case.     

基于弹流润滑的滚子轴承参数研究

基于弹流润滑理论研究滚子轴承结构参数对其润滑特性的影响。结合弹性接触变形方程以及流体动力学润滑方程,建立适合于滚子轴承的弹流润滑模型,研究在不同椭圆率、载荷、卷吸速度以及黏度等因素作用下滚子轴承的摩擦学性能变化规律。结果表明：椭圆率、载荷、卷吸速度以及黏度会不同程度地影响压力峰值及二次压力峰等参数;随着椭圆率的增大,油膜厚度以及压力显著增大;随着载荷的增大,总体压力、压力峰值、二次压力峰及其尖锐度明显增大,但最小油膜厚度略有下降;黏度与最小油膜厚度以及压力存在着明显正相关关系;卷吸速度与油膜厚度存在着微弱正相关关系,与油膜压力存在着微弱负相关关系。因此,一定程度上增大椭圆率并减小载荷,有利于提高润滑性能。     

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.