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.     

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。     

基于动态子结构的主轴承热弹性流体润滑研究

研究基于动态子结构缩聚的轴承热弹性流体动力学(TEHD)基本理论和求解方法;建立某V型8缸内燃机主轴承的TEHD仿真模型,分别计算得到各主轴承在最大载荷工况下的油膜压力、油膜厚度、摩擦功耗、轴心轨迹和油膜温度等润滑特性;针对润滑状况较差的第3主轴承,进行TEHD、EHD(弹性流体动力学)和HD(流体动力学)不同仿真求解方法的对比研究。研究结果表明,该内燃机的第3主轴承最小油膜厚度和最大油膜压力等润滑性能最差,需要进行相应的改进设计;TEHD求解中计及了润滑油和轴瓦热效应的影响,能获得更高的轴承润滑特性计算精度。     

铝锡轴瓦的疲劳裂纹分析

对AlSn20Cu轴瓦进行了疲劳试验,观察到疲劳裂纹的萌生及扩展过程,并以计算所得轴心轨迹、油膜压力和合金层应力分布为依据,分析了轴瓦的疲劳过程,与试验结果相吻合,从而为轴瓦的疲劳裂纹分析提供了新的研究方法。     

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。     

轴瓦变形时转子系统的动力学特性

针对常见的轴瓦畸变故障，通过试验对比分析不同轴瓦形状、具有偏心质量及耦合故障时转子系统的动力学特性，结果表明：低转速下的试验结果易受试验台本身的影响；轴瓦变形、质量偏心及耦合故障的存在均会导致振动幅值较正常轴瓦增大；轴心轨迹可以反映轴瓦畸变，根据突变幅值和轴心轨迹可以定性判断畸变特征；耦合故障的存在会使系统运行处于不利状态。     

车用汽油机轴承润滑可靠性研究

为实现车用发动机轴承工作可靠、耐久目的,应用摩擦学理论及发动机CAE技术对现有机型曲柄连杆机构工作过程进行分析,研究轴承间隙极限状态下轴承比压、轴心轨迹、最小油膜厚度随发动机转速的变化关系,从中对轴承润滑可靠性进行评价。研究结果表明,在发动机本体及边界条件未变下,曲轴主轴承最小油膜厚度随转速增大而减小,连杆大头轴承则随转速增大先增大后减小,最大轴承间隙下的最小油膜厚度比最小间隙下大40%,轴承均未出现干摩擦现象,波纹状轴瓦润滑性能优于平状轴瓦。     

仿真技术在静压轴承系统中的应用

在流体机械中,流场测试设备昂贵,计算流体力学(CFD)成为设计和模拟仿真的有效手段.因此采用有限元法,借助相关软件和所编制的子程序通过数值计算得出了一定负载下球磨机静压轴承的油腔压力并分析了轴瓦回油槽对承载能力的影响,得出油膜内压力分布和速度分布.     

动载滑动轴承疲劳失效过程研究

研究了动载滑动轴承疲劳失效过程,观察到轴瓦表面裂纹、第二相裂纹等类型。通过润滑计算得到轴心轨迹、油膜压力和合金层应力分布,对轴瓦失效过程进行了分析,结果表明,轴怕疲劳裂纹由轴瓦宏观应力分布和微观应力集中共同作用,当基体与第二相的Ｅ、μ相关工不多时,应力集中不明显,当基体与第二相的Ｅ、μ相差较多时,应力集中产生的影响不可忽略。     

求解内燃机曲轴—轴承轴心轨迹的动力学方法

曲轴—轴承是不可分割的系统,这个系统一旦运转起来以后,它的各种机械行为必然是同时发生并相互影响的。基于这种理念,提出的求解曲轴—轴承轴心轨迹的方法是：联立求解曲轴动力学方程和轴承润滑方程,得到作用于轴承上的载荷和曲轴动力学响应(轴心轨迹),再通过进一步地润滑分析得到轴承的摩擦学特性。与静力学方法获得两维轴心轨迹相比,动力学方法分析计算得到的曲轴轴心轨迹是三维的,并可以得到曲轴轴心轴向运动轨迹。此外,两种方法求得的轴承最小油膜厚度和最大油膜压力也不相同。导致不同计算结果的原因是由于曲轴系统动力学效应引起的。     

Flow Ripple of Axial Piston Pump with Computational Fluid Dynamic Simulation Using Compressible Hydraulic Oil

The flow ripple, which is the source of noise in an axial piston pump, is widely studied today with the computational fluid dynamic(CFD) technology development. In the traditional CFD modeling, the fluid compressibility, which strongly influences the accuracy of the flow ripple simulation results, is often neglected. So a compressible sub-model was added with user defined function(UDF) in the CFD model to predict the flow ripple. At the same time, a test rig of flow ripple was built to study the validity of simulation. The flow ripple of pump was tested with different working parameters, including the rotation speed and the working pressure. The comparisons with experimental results show that the validity of the CFD model with compressible hydraulic oil is acceptable in analyzing the flow ripple characteristics. In this paper, the improved CFD model increases the accuracy of flow ripple rate to about one-magnitude order. Therefore, the compressible model of hydraulic oil is necessary in the flow ripple investigation of CFD simulation. The compressibility of hydraulic oil has significant effect on flow ripple, and the compression ripple takes about 88% of the total flow ripple of pump. Leakage ripple has the lowest proportion of about 4%, and geometrical ripple leakage ripple takes the remnant 8%. Besides, the influence of working parameters was investigated through the CFD simulations and experimental measurements. Comparison results show that the amplitude of flow ripple grows with the increasing of rotation speed and working pressure, and the flow ripple rate is independent of the rotation speed. However, flow ripple rate of piston pump grows with the increasing of working pressure, because the leakage ripple will increase with the pressure growing. The investigation on flow ripple of an axial piston pump using compressible hydraulic oil provides a more validity simulation model for the CFD analyzing and is beneficial to further understanding of the flow ripple characteristics in an axial piston pump.     

Oil whip-induced wear in journal bearings

This paper investigates the effect of oil whirl and oil whip in fluid film radial bearings due to possible metallic contact. The degree of metallic contact and thereby wear and tear between rotating shafts and bearing bushes is assessed by measuring electric currents through the oil film. The current as well as the voltage varied in accordance with the contact ratio between the shaft and bush in the fluid film radial bearing. The gauge signal thus indicates the degree of metallic contact based on the thickness of the oil film in the load zone. Some experimental results are provided to illustrate that at low normalised loads involving oil whirl and oil whip, no electric current is detected, while high levels of electric current are registered at high load levels when no oil whirl or oil whip occurred. It is therefore concluded that at low loads, oil whirl and oil whip have little influence on wear and tear in a journal bearing.     

链条套筒与销轴铰链副冲击载荷-往复运动的弹流润滑数值模拟

数值模拟链传动中销轴与套筒之间的定载荷和变载荷弹流润滑接触问题,套筒相对于销轴做纯滑动往复运动。定载荷是假定往复运动过程中载荷恒定不变;变载荷是假定链节在啮入和啮出链轮过程中存在的冲击载荷按正弦函数规律变化。比较在定载荷和变载荷加载条件下线接触往复运动工况的弹性润滑油膜变化情况,分析在动载荷加载条件下不同行程长度对弹性流体动力润滑特性的影响。研究发现,动载荷对油膜的压力、膜厚影响较大:随着动载荷的增加,油膜中压力急剧增大,膜厚减小;但加载方式对摩擦因数的影响不大;在相同的加载方式下,随着行程长度的增加,油膜压力减小,中心膜厚和最小膜厚显著增加。     

An analysis of the lubrication mechanisms of the bush-type bearings in high pressure pumps

The paper examines the behaviour of the bushes in high pressure ‘bush configuration’ gear pumps. Experimental measurements of the clearances between the end-faces of the gears and the bushes are presented and an analysis of the mechanism of lubrication is given. It is suggested that bush lubrication depends on the surface irregularities at the ends of the gears and on the non-flatness of the bushes.     

高炉TRT发电机轴瓦振动故障诊断与处理

针对我公司4#高炉煤气系统TRT发电机组换型改造后试车轴瓦振动大,通过对机组振动数据采集分析,准确判断故障,消除了发电机组轴瓦振动故障,保证设备安全运行。     

离心压缩机轴位移故障自愈调控系统试验研究

通过总结轴位移故障的特征,分析研究可倾瓦推力轴承的力学性能,提出一种在线预测和诊断轴位移故障的方法,通过试验实现轴位移故障自愈。离心压缩机的轴位移故障大多带有突发的特点,这种突发是由于推力盘和轴瓦之间的油膜破裂导致的。这种破裂可能是润滑油油质变差或者油压降低导致油膜承压能力严重降低,达到一定门槛值后,油膜破裂;也可能是离心压缩机在工艺工况波动时,转子轴向力增大超过了油膜的承载能力,从而导致油膜破裂。不管哪种故障都会导致轴瓦的严重磨损,压缩机紧急停车。通过在线的检测推力轴承的油膜刚度,区分导致轴位移增加是否由轴向力引起,并且引入轴位移故障自愈调控机制,以轴位移为控制参量,实时调控转子的残余轴向力,保证推力轴承的最小油膜厚度。试验研究表明,该机制能够有效的实现离心压缩机轴位移故障的自愈。     

螺杆泵斜-平面固定瓦推力轴承润滑特性分析

为了提升润滑油系统可靠性,避免轴承磨损,采用CFD分析螺杆泵斜-平面固定瓦推力轴承的润滑特性。计算该螺杆泵螺杆轴向力,得到油膜承载力数值范围;采用有限差分法得到油膜压力分布与厚度分布,采用有限体积法仿真分析不同油膜厚度、不同进油温度时轴承的压力场。仿真结果表明：温度通过影响润滑油黏度对轴承压载产生影响,当油膜厚度固定时,进油温度越低,润滑油黏度越大,轴承所受压载越大;当进油温度一定时,油膜厚度降低,则承载能力增加。因此,在低温启动滑油泵时,油膜由薄变厚平衡螺杆轴向力的过程中,轴承压载可能会超过许用压载,从而导致轴承磨损。     

3D Two-way coupled TEHD analysis on the lubricating characteristics of thrust bearings in pump-turbine units by combining CFD and FEA

The thermal elastic hydro dynamic(TEHD) lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis(FEA). But it is still a problem to conduct the computation by combining computational fluid dynamics(CFD) and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.     

计入热弹变形的周隙密封性能研究

对周隙密封进行热弹流研究,分析周隙密封的流场、压力场和温度场。计入热弹变形的作用,比较不同参数如转速和不同密封瓦材料等因素对密封性能的影响。研究表明:密封瓦热膨胀变形非常显著,密封瓦体的热变形为向瓦体外部膨胀,使密封瓦油膜间隙变大,泄流量增大;随着转速的升高,密封瓦的侧泄流量和温升均迅速增加;使用热膨胀率较低的碳碳复合材料,将使密封瓦的侧泄流量和功耗大大降低。     

Steady-state thermo-hydrodynamic analysis of cylindrical fluid film journal bearing with an axial groove

A steady-state thermohydrodynamic analysis of an axial groove journal bearings in which oil is supplied at constant pressure is performed theoretically. Thermohydrodynamic analysis requires simultaneous solution of Reynolds equation, energy equation and heat conduction equations in the bush and the shaft. From parametric study it is found that the temperature of the fluid film raises due to frictional heat thereby viscosity, load capacity decreases. Increased shaft speed resulted in increased load carrying capacity, bush temperature, flow rate and friction variable. It is difficult to obtain the solution due to numerical instability when the bearing is operated at high eccentricity ratios.