基于AVL-EXCITE的内燃机连杆轴承润滑仿真分析

内燃机连杆轴承的润滑状况对连杆轴承的使用寿命影响很大。随着内燃机的不断强化,对连杆轴承性能的要求也相应提高。因此,深入研究连杆轴承的润滑问题以便更加准确地分析和设计轴承的性能便显得日益重要。首先从理论上阐述了润滑状况对轴承工作可靠性的影响,然后针对某发动机的连杆,在AVL-EXCITE中建立了连杆的柔性多体动力学与动力润滑耦合仿真模型。通过计算得到了连杆轴承的轴心轨迹、最小油膜厚度和最大油膜压力等参数,并比较了转速、轴承间隙和温度对轴承润滑性能的影响。研究结果对连杆轴承动力学耦合分析和优化设计以及判断轴承工作的可靠性具有重要意义。     

循环冲击载荷作用下滚滑轴承滚子的润滑特性研究

为探究冲击载荷对滚滑轴承润滑性能的影响,设计一种轮子扁疤系统,以模拟轴承受到的循环冲击载荷,利用数值分析法对比研究冲击载荷作用下滚滑轴承的润滑特性及不同工况对滚滑轴承滚子润滑的影响。结果表明：滚滑轴承的滚子润滑受冲击载荷的影响小于滚动轴承;冲击载荷发生前,滚滑轴承滚子油膜有高于油膜中心压力的第二峰值压力,油膜出口区有明显缩颈现象,随冲击载荷的增大,第二峰值压力虽会逐渐减小,但不会消失;冲击载荷频率越大,最小油膜厚度越大,冲击载荷幅值越大,滚子油膜厚度越薄;滚子油膜厚度随润滑油黏度、转速的增加而增加。     

超临界二氧化碳涡轮机主轴静压轴承承载特性分析

以超临界CO2涡轮机主轴支承静压轴承为研究对象,基于Fluent软件建立静压轴承气膜的三维分析模型,分析了轴承结构、偏心率、气膜间隙对气膜压力、承载力和刚度的影响.结果表明:双排进气结构静压轴承的气膜压力、承载力和刚度均高于单排进气结构;偏心率对承载力有显著的影响,承载力和偏心率呈非线性正相关;在偏心率一定的条件下,平...     

冲击载荷作用下计入轴倾斜的轴-轴承系统动力学摩擦学行为研究

以多柔体动力学分析为基础,通过ADAMS与Matlab联合仿真,研究在冲击激励力作用下计入轴受载变形倾斜时弹性轴-轴承系统的动力学和摩擦学行为。得到的主要结论是:间隙较大时,轴-轴承系统发生自激振动;计入轴受载变形倾斜,轴承的最大油膜压力大幅度上升,最小油膜厚度大幅度下降。     

考虑油膜润滑的轮毂轴承弯曲疲劳寿命预测与分析*

为精确分析预测某型轿车轮毂轴承的弯曲疲劳寿命,考虑轴承工作状态下游隙与油膜厚度的关系,以及温度对游隙和油膜厚度的影响,结合点接触弹流油膜厚度计算方法,精确计算其最小油膜厚度值;根据ISO提供的对Lundberg-Palmgren寿命模型修正方法,计算油膜参数和润滑剂黏度比,从而确定修正系数,建立改进的寿命模型。为了验证改进模型的正确性,使用旋转弯曲疲劳寿命试验机进行疲劳试验,试验结果在误差合理区间内,证明研究模型的可靠性。建立轮毂轴承载荷分布分析模型,讨论中心距对最大滚动体载荷的影响,研究轮毂轴承的疲劳寿命在不同纯弯矩载荷和不同车速下随中心距的变化规律。结果表明：弯矩载荷是影响疲劳寿命的主要因素,增加中心距可以延长轴承寿命;轴承润滑条件与轴承转速有关,在一定范围内,转速越高,其内部润滑越充分,使用寿命越长。     

乏油条件下乳化液润滑复合塑料轴承等温弹流润滑分析

塑料轴承是常用的水润滑轴承,而乳化液由于无污染、来源广、节省能源、安全性等特点成为一种具有良好应用前景的润滑剂.以乳化液润滑复合塑料轴承为研究对象,建立塑料轴承弹流润滑模型,分析乏油条件下转速和载荷对润滑膜膜厚的影响,并与充分供油条件下的润滑膜膜厚进行比较.结果表明:随着供油量的增加,轴承油膜膜厚增加,但当供油量超过一临界值时,油膜膜厚不再变化.在乳化液润滑条件下,膜厚及最小膜厚均随转速的增大而明显增大,随载荷增大而减小,且供油条件没有造成明显的影响.     

Coefficient of friction and oil flow in plain finite partial journal bearings during turbulent operation

Bearings which have been properly designed with respect to the provision of a hydrodynamic oil film can sometimes fail by overheating. Hence the complete analysis of journal bearings requires the evaluation of friction and oil flow. Plain partial journal bearings of finite length with a turbulent hydrodynamic film of a newtonian lubricant were analysed to obtain the coefficient of friction and the total oil flow. The coefficient of friction, which is a performance characteristic, is presented analytically in the closed form. The total oil flow through superlaminar bearings is also considered as a bearing performance characteristic. All the results of interest are dimensionless and available in a closed form which is simple yet exact over the wide range of parameters involved.     

A study on the sound of roller bearings operating under radial load

The purpose of the paper is to numerically investigate the sound characteristics of roller bearings operating under radial load. For the sake of simplifying the analysis, it was assumed that the roller bearings are infinitely long, a noise source due to pressure fluctuation of oil film is taken as a line noise source, and acoustic energy losses in the bearing are neglected. To obtain sound characteristics of the bearing, the rolling contact load and the sound pressure level distributions were calculated for various operating conditions, and the results were compared with each other. How much the bearing noise can be affected by the design parameters, such as radial clearance of the bearing, viscosity of lubricant, and the number of rollers was also investigated. The results and discussions of the present paper could aid in the design of low-noise roller bearings and to solve the noise problems related to such bearings.     

不同节流方式的滑动轴承油膜静态性能求解

针对毛细管、小孔、滑阀反馈和薄膜反馈4种节流方式,结合三油腔动静压混合油膜轴承及四油腔静压轴承,建立了轴承油膜静态性能求解的数学模型。从Reynolds方程的离散、间隙函数数学模型的建立、边界条件的确定、连续性方程的建立、不同节流方式的进油流量数学模型的推导、轴承的承载能力及温升等方面分析了轴承油膜静态性能的求解。计算结果表明:采用毛细管和小孔节流轴承的承载能力和油膜刚度较低;而采用滑阀反馈和薄膜反馈节流轴承具有较高的油膜刚度和承载能力。     

Turbulent Journal Bearings: Dimensionless Steady-State Performance Charts for the Two-Axial Groove Case

Under conditions of high sliding speed, the lubricant film in hydrodynamic bearings becomes turbulent, and large errors can occur if analysis and design are then based on the commonly used laminar theories.

One method of taking into account turbulence in the oil film is to use a modified form of Reynolds equation. Such an equation tins been used to produce dimensionless performance data for journal bearings with two axial grooves.

These data are presented in graphical form in order to give a direct appreciation of the effects of turbulence on dimensionless characteristics and also in tabular form to permit the data to be incorporated into full design procedures.     

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。     

Dynamic analysis of a reciprocating compression mechanism considering hydrodynamic forces

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gümbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.     

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.     

可控节流参数对液体静压轴承特性的影响研究

节流器是液体静压主轴的核心元件,其节流特性对液体静压主轴的刚度和回转精度具有直接影响。针对现有节流器在主轴工作时节流特性不可控的不足,提出一款预压预调型可控节流器。在分析可控节流器工作原理和节流特性基础上,根据流体润滑理论,建立基于可控节流器的液体静压轴承承载性能的理论模型,研究可控节流器供油压力、弹簧刚度和控制油腔压力等参数对液体静压轴承承载性能的影响规律,并与固定节流液体静压轴承的承载性能进行对比。研究发现,在其他结构参数及工作参数一定的条件下,可控节流器能够显著地提高液体静压轴承的油膜刚度;在不同偏心率条件下,可控节流液体静压轴承的最佳油膜刚度对应的节流参数不同。在开发的液体静压电主轴试验台上进行了试验研究,通过对油腔压力和油膜刚度的理论计算值与试验测量值的对比,证实了可控节流方案的有效性。     

Oil film thickness measurement by means of an optic lever technique

Oil film thickness in hydrodynamic bearings is a fundamental parameter influencing overall hydrodynamic bearing performance. Knowledge of this thickness allows bearing performance to be optimised. For the small hydrodynamic bearings that are usually used in laboratory test facilities, a very small sensor (e.g.,<2 mm) is required because of space limitations. Commercially available eddy‐current and capacitance sensors are too large to be mounted in the pad of such a bearing. An alternative approach is to use sensors based on optical methods, such as the optic lever technique. The main idea in this technique is to detect the intensity of a light beam reflected from a target surface. This intensity is a function of the distance between the sensor and the target. This paper reports the specific features of the optic lever technique as used for measurements of oil film thickness. The design, calibration procedure, and main characteristics of an optical sensor are discussed. A test rig for the calibration of oil film thickness sensors is also presented. The sensor response curve has two parts, linear and non‐linear; using the linear part results in high sensitivity in the micrometre range. The influence of different types of oil on the output signal of the sensor has also been investigated. Experiments with different target velocities have shown that this sensor can be used for accurate and reliable measurement of oil film thickness in hydrodynamic bearings.     

Theoretical and experimental investigations of a variable- impedance hydrodynamic bearing

The aim of the work described in this paper is to develop a hydrodynamic bearing whose oil film dynamic stiffness and damping coefficients could be tuned to take on low values, without upsetting the bearing steady load carrying capacity, in order to obtain an improved dynamic response for machines running in such bearings. It was required that this tuning of the bearing dynamic characteristics could be carried out after assembly of the machine in question, and if necessary while the machine was in operation.A theoretical analysis of the new design of bearing was carried out, based on a finite-difference model of the bearing oil film. This analysis enabled the steady-state load carrying capacity of the bearing to be calculated for any particular running conditions. The oil film stiffness and damping characteristics were then calculated using the finite-displacement technique; these were then used to calculate the unbalance response of a flexible rotor running in such bearings. Experimental measurements of the unbalance response of a model rotor running in the new bearing design were also recorded, and compared with similar measurements obtained when conventional bearings were used.Both theoretical and experimental results show that the proposed new bearing design has a similar steady load carrying capacity to that of conventional hydrodynamic bearings, but that the unbalanced response and force transmissibility of machines running in the new design of bearing are substantially superior to that obtained with conventional bearings.     

重载静－动压油膜轴承随机监控理论探讨

讨论重载静－动压油膜轴承运行工况评估与监控的方法与途径。介绍静－动压油膜轴承的结构与工作特点；在理论分析与数值计算的基础上，绘制了３种工作制度下的油膜压力分布主体图；结合实践与实测，给出安全运行判据，并以实例进行演示；最后，制订了评估与监控的过程框图。     

Analysis of the dynamics of a slider-crank mechanism with hydrodynamic lubrication in the connecting rod-slider joint clearance

The conventional slider-connecting rod-crank mechanism is widely applied in mechanical systems. The use of hydrodynamic bearings in the mechanism joints is of particular interest in reducing friction, mainly in special conditions of lubrication such as the connecting rod-slider joint. This bearing belongs to a class of bearings with alternating rotational motion. This paper proposes a mathematical model for this particular problem, considering the dynamics of the slider-connecting rod-crank system interacting with the lubrication phenomenon in bearings with alternating motion. Two models were used to analyze the dynamics of the system. The first model (by Eksergian Equation of Motion) represents the system when the connecting rod end is in contact with the bearing surface, assuming, in this condition, the same behavior as that of rigid bearings (without clearance). The second model (by Lagrange Method) represents the system when the connecting rod end is in the hydrodynamic lubrication mode in the slider bore clearance. In this condition, the slider moves in relation to the connecting rod, presenting a problem of multi-degrees-of-freedom. The mathematic model of hydrodynamic lubrication was introduced to obtain more realistic results of the system's dynamic behavior.     

Lubrication of a narrow porous journal bearing with a couple stress fluid

This paper describes a theoretical investigation of the rheological effects of couple stress fluids on the performance of narrow porous journal bearings. A most general modified Reynolds equation is derived for narrow porous journal bearings using the Stokes constitutive equations for couple stress fluids. The fluid in the film region and in the porous region has been modelled as a couple stress fluid. The analysis takes into account velocity slip at the porous interface using the Beavers‐Joseph criterion. A closed‐form expression for field pressure is obtained for narrow journal bearings. Eigen‐type expressions for field variations are obtained. The dimensionless load‐carrying capacity, attitude angle, and coefficient of friction are presented for different operating parameters. It is observed that narrow porous journal bearings with couple stress fluids as lubricant show a significant increase in load‐carrying capacity with reduced coefficient of friction as compared to the Newtonian case. The present study predicts the effects of the percolation of polar additives (microstructures) into the porous matrix on the bearing performance.     

Effect of slip flow in aerostatic porous rectangular thrust bearings

A theoretical analysis of the static characteristics of aerostatic porous rectangular thrust bearings with uniform film thickness is presented. A modified form of the Beavers-Joseph slip velocity boundary condition is applied at the interface of the porous pad and the lubricating film. When the thickness of the pad is small compared with the other two dimensions, the pressure distribution in the porous media is obtained in closed form and the modified Reynolds equation can be solved numerically by the finite difference method. The load capacity, mass flow rate of the gas and static stiffness are expressed in dimensionless form and calculated numerically for different operating parameters. Velocity slip reduces the load capacity and the mass flow rate of the gas and depends on the feed parameter for its effect on stiffness.