四瓦可倾瓦轴承瓦块摆动特性

以第四代核电机组高温气冷堆氦风机导轴承为对象,系统研究四瓦可倾瓦轴承的瓦块摆动特性。理论推导得出量纲一瓦块摆角取决于轴承结构参数、预负荷和偏心率,但是与轴承间隙比、轴颈转速和润滑油黏度无关。数值分析表明:瓦块摆角特性由瓦块与载荷周向相对位置、预负荷和偏心率决定。轴承结构参数确定时,与载荷正对瓦块的摆角曲线的形状取决于预负荷,预负荷小于0.5时其摆角随偏心率增大先增加后减小,预负荷大于0.5时摆角则随偏心率的增大而逐渐减小;与载荷侧对瓦块的摆角在预负荷较小时随偏心率增大一直增大或减小,预负荷较大时则随偏心率的增大先保持不变然后减小。瓦块摆角对最小油膜厚度影响很大,瓦块摆角可能为负值,从而使最小油膜厚度较固定瓦时的最小油膜厚度偏大。研究结果为氦风机安全运行分析提供了依据。     

带有挠性弹簧的大型可倾三瓦径向滑动轴承稳定工作点的确定

本文结合一个实际的、具有挠性弹簧的大型可倾三瓦轴承分析了弹簧预紧力对轴承预加负荷及轴承工作点的影响,并说明了如何根据弹簧的特性曲线求轴承的实际工作点。计算结果表明:考虑弹簧预紧力后,轴承的承载能力增加,工作偏心减小;但主承载瓦(二瓦)因摆角增大,最小油膜厚度有所减小;轴承偏位角明显减小;轴心向右偏移(偏向载荷作用线),使侧瓦负荷减轻.     

制造误差对多瓦可倾瓦径向滑动轴承热流体动力润滑性能的影响

建立考虑制造误差的多瓦可倾瓦径向滑动轴承热弹流润滑(TEHD)分析的计算模型,计算得到有制造误差时的瓦块油膜厚度、油膜压力、瓦面温度分布等,并对比分析多瓦可倾瓦径向滑动轴承在有无制造误差时的热弹流润滑性能差异。结果表明,轴径误差会导致最大油膜压力显著增大,轴瓦瓦面曲率半径误差会导致最小油膜厚度和最大油膜压力均有一定增大,而预载荷误差对轴承的润滑性能无明显影响。     

高速齿轮传动可倾瓦轴承预负荷系数影响研究

可倾瓦轴承因其稳定可靠的特点被广泛应用于现代工业,相关研究也蓬勃发展起来,但目前关于可倾瓦轴承预负荷系数的研究主要集中在低转速领域。以DyRoBeS软件为研究工具,取普遍使用的5块瓦可倾瓦轴承作为研究对象,分析在20 000 r/min、40 000 r/min、60 000 r/min的高转速工况下,预负荷系数对可倾瓦轴承工作性能的影响,为高速齿轮传动中可倾瓦的设计应用提供理论依据。预负荷系数从0.1增加至0.7的过程中,对功率损失影响不大,使最大油膜压力与刚度系数增加,最小油膜厚度与阻尼系数减小。预负荷系数的混合设置会影响各瓦块压力分布,同时使最小油膜厚度以外的轴承性能参数明显增加。所得结论对高转速可倾瓦轴承的优化设计起到积极的作用。     

固定-可倾瓦轴承支撑的转子的非线性动力学特性

以固定-可倾瓦轴承支撑的单盘柔性转子为研究对象,根据转子动力学理论建立了其动力学模型。基于动态Reynolds方程和边界条件,运用Castelli法求解Reynolds方程,在单瓦坐标系下建立了单块轴瓦的非线性油膜力数据库。经过坐标变换,组装计算最终获得固定-可倾瓦轴承的油膜力。在计算油膜力的时候考虑两种情况,即考虑瓦块转动惯量和忽略瓦块转动惯量。首先将这两种情况下转子的运动轨迹进行比较,然后这种分析了考虑瓦块转动惯量时转子的动力学行为,同时也比较了在不同的预负荷和支点比的情况下转子的运动轨迹和可倾瓦瓦块的摆角。     

考虑滑移效应的可倾瓦动压气体轴承承载性能分析

以可倾瓦气体轴承为研究对象,考虑滑移效应对可倾瓦动压气体轴承的气膜压力分布和承载力的影响,在1阶滑移和WU新滑移速度边界条件下推导修正雷诺方程的基础上,使用有限差分法求解不同瓦块偏心率、轴承数下的承载力。结果表明：随着偏心率、预载系数、轴承数的增大,轴承承载力增大;滑移边界条件下计算出的可倾瓦动压气体轴承的承载力显著降低;相同条件下,基于WU新滑移边界模型计算所得承载力最小,结果明显低于连续介质模型和1阶滑移模型。     

可倾瓦气体动压轴承参数对其承载能力影响的分析与研究

本文介绍了可倾瓦气体动压轴承承载能力的计算方法,分析了轴承参数对其承载能力的影响,对瓦块支承为刚性、弹性及其组合的可倾瓦轴承的特点进行了阐述,并以设计曲线的形式给出了计算结果。     

刚性和弹性支撑可倾瓦推力轴承稳态特性分析

建立刚性球头支撑和弹性橡胶垫支撑可倾瓦推力轴承热弹流耦合模型；在弹性橡胶垫支撑可倾瓦推力轴承橡胶垫的弹性变形分析中采用了变形协调矩阵方法，以协调匹配橡胶垫变形和水膜厚度分布，同时在搜索稳态解的过程中引入模拟退火算法；基于变分原理求解Reynolds方程，得到了轴承水膜压力分布，并比较2种推力轴承在转子存在角不对中时的静特性。结果表明：理想工况下，刚、弹支可倾瓦推力轴承稳态特性没有明显区别；当转子存在不对中时，刚性球头支撑可倾瓦轴承在不同瓦块之间受力偏载严重，进而导致瓦面最小水膜厚度过小，瓦块容易出现磨损，而弹性支撑瓦不同瓦块之间水膜力分布更均匀，利于轴承的长期可靠运行。     

波箔型径向气体轴承静态特性分析

建立考虑气体可压缩性和箔片变形的波箔型轴承气膜厚度模型,采用有限差分和松驰迭代法耦合求解Reyn olds方程和气膜厚度方程,得到波箔型轴承气膜厚度和气膜压力分布,并分析波箔型动压径向气体轴承结构参数和运行参数对其静态性能的影响.结果表明:波箔型轴承数值分析结果与相关文献试验数据相符度较好,证明该模型的科学性与精确性;对比箔片轴承和传统刚性表面轴承气膜压力和气膜厚度的分布特点,表明箔片轴承具有更高的承载能力;随着偏心率、转速的增大,箔片轴承承载能力增大,偏位角减小;随着转速增大,气膜压力提高,箔片变形增大,最小气膜厚度增大.     

瞬变载荷作用下五瓦可倾瓦滑动轴承特性分析

为了研究动压五瓦可倾瓦滑动轴承在瞬变载荷作用下的动态行为,在考虑轴颈惯性力和非惯性力的基础上,建立可倾瓦滑动轴承的轴心轨迹方程,利用有限单元法求解油膜压力,采用欧拉法求解有限长滑动轴承瞬时轴心轨迹;研究不同预负荷下偏心率与瓦块姿态角的变化关系,以及在阶跃载荷和正弦脉冲载荷作用下轴心轨迹、瓦块摆角及轴颈所受合力变化规律。结果表明:在瞬变载荷作用时,轴心轨迹、瓦块姿态角及油膜合力都有较大的变化并呈现出一定的振荡过程;由于脉冲载荷的作用时间有限,随着其消失,轴心仍收敛于原平衡位置,而阶跃载荷则使轴心收敛于新的平衡位置;相同条件下的可倾瓦轴承比固定瓦轴承具有更好的稳定性。     

Analysis of heavy duty tilting-pad journal bearing taking into account pad distortion and possible adoption of rubber pad segments

In this work a comparative study has been made between the thermo-hydrodynamic performance of a three shoe tilting-pad journal bearing with rigid and elastic pads subjected to unbalance load. A case study of a bearing adopting three rubber pad segments has also been studied. The distortion of the elastic pad is introduced into the distribution of the film thickness through an iterative scheme to assess its effect on the load carrying capacity of the bearing. A finite element mesh is used to calculate the distortion of the elastic pad while a finite difference mesh is used to calculate the pressure field in the lubricant film. Results have shown a number of interesting conclusions regarding the adoption of rubber pad segments instead of tilting-pads. There is an increase in minimum oil film thickness when using elastic pad or even rubber pad segments compared with rigid pads. Also the maximum pressure and load carrying capacity are not significantly affected.     

Measured Performance of Tilting-Pad Journal Bearings over a Range of Preloads—Part I: Static Operating Conditions

This article presents the measured static characteristics for five tilting-pad journal bearings with a range of preload factors. The bearings had five shoes with static forces applied both on the pad and between pads. The journal diameter was 70 mm, with a length-to-diameter ratio of 0.75, a pivot offset ratio of 0.50, and a nominal assembled radial clearance of 81.3 μm. The rocker-backed pads have nominal radial machined clearances of 176.8, 114.3, 91.4, 73.7, and 61.0 μm. These clearances constitute a range of preloads from ?0.333 to 0.540. Most tilting pad bearings are intentionally designed with positive preloads, although with pivot wear and/or pad and pivot distortion or machining tolerances, bearings can operate with zero or negative preloads. Measured results for bearings with negative preload factors have not previously been available. Measurements reported here were made for a variety of speed-load conditions encompassing a Sommerfeld number of 0.1 to 4.5. The measured parameters are eccentricity magnitude, attitude angle, film thickness, and temperatures sufficient to define thermal boundary conditions. Also measured are oil supply pressure, flow rate, and on-shaft pressure profiles. The focus of the work presented herein is to quantify the influence of preload on film thickness, maximum pad temperature, and eccentricity magnitude and attitude angle. Measurements showed preload had a moderate influence on operating eccentricity but not on attitude angle. Negative preloads resulted in the greatest temperature rise, although all temperature rises were relatively small.     

Dynamic stiffness and damping coefficients of aerodynamic tilting-pad journal bearings

The dynamic gas–film forces of aerodynamic bearing often can be characterized by eight linear stiffness and damping coefficients. How to theoretically predict these coefficients is a very difficult issue for tilting-pad gas bearing design because of its structural complexity. The current study presents a novel and universal theoretical analysis method for calculating the dynamic stiffness and damping coefficients of aerodynamic tilting-pad bearing. The gas–film pressure within the bearing is expressed in the form of dimensionless compressible gas-lubricated Reynolds equation, which is solved by means of the finite element method. With the assumption that the journal and the pads are disturbed with the same frequency, the dynamic coefficients of tilting-pad gas bearing are computed by using the partial derivative method and the equivalent coefficient method. Finally, the investigations are conducted about the effects of bearing number, perturbation frequency of the journal and the pads, eccentricity ratios, preload and length-to-diameter ratio of the bearing on the dynamic coefficients of aerodynamic tilting-pad journal bearing. The numerical results indicate that the dynamic stiffness and damping coefficients of tilting-pad gas bearing are closely related with these factors. The proposed analytical method provides a valuable means of predicting dynamic performances of tilting-pad gas bearing. The solution can be used for the purpose of prediction of dynamic behavior of the rotor systems supported by aerodynamic tilting-pad bearings.     

Numerical analysis on the static performance of tilting pad–journal gas bearing in subsystems

For tilting pad–journal bearing, each pad and the journal form a subsystem with its own local parameters reflecting the relative position of the journal and pad. In this paper, tilting pad–journal gas bearing has been studied numerically in perspective of subsystems to prevent pad spragging. The effect of eccentricity, preload and gas compressibility on local parameters have been studied in this fluid–solid coupled problem. Finite element method is adopted to solve the compressible Reynolds equation, and the load between pads configuration is chosen as a specific example.     

多叶动压气体滑动轴承静态特性的有限差分算法

多叶动压气体滑动轴承因其结构简单、摩擦阻力低、旋转精度高和无环境污染等优点,在高速离心分离机、空气压缩机和透平膨胀机等旋转机械中应用广泛。为探究多叶动压气体滑动轴承的静态性能,通过数学变换将三叶动压轴承的气体润滑Reynolds方程转化为标准偏微分方程形式,利用有限差分法和超松弛迭代法进行数值求解,研究气膜厚度和气膜压力分布、承载力、摩擦因数和质量流量等静态性能,随偏心率、预负荷系数、轴承数、长径比及瓦块分布位置的变化规律。结果表明：三叶轴承的承载力和轴颈表面摩擦因数随偏心率和长径比的增加而增加,而偏位角和质量流量随偏心率和预负荷系数的增加则呈现出相反的变化趋势;随着轴承数和预负荷系数的增大,承载力和摩擦因数显著提高,偏位角和质量流量则逐渐减小;瓦块分布位置对三叶动压气体滑动轴承的静态性能影响显著,其中瓦上承载方式的承载力、偏位角和质量流量明显高于瓦间承载方式。     

多瓦可倾瓦径向滑动轴承热润滑性能分析

考虑变黏度、密度的情况,建立多瓦可倾瓦径向滑动轴承的数学模型,用有限差分法求解其热流体动力润滑(THD)模型,分别计算12块瓦可倾瓦径向滑动轴承的最小油膜、压力分布和三维温度场分布,分析不同载荷、不同转速、不同润滑油黏度等对轴承各瓦的热润滑性能影响。结果显示,建立的模型及其计算程序能计算分析多瓦可倾瓦径向滑动轴承的热润滑问题。润滑油黏度和转子转速对多瓦可倾瓦径向滑动轴承的热润滑性能有较大的影响;瓦块绕支点的倾斜以及瓦块所处的角度位置会影响部分瓦块的热润滑性能,出现与普通圆形径向滑动轴承不一致的润滑性能变化。     

静压孔位置对油膜支承可倾瓦轴承承载性能的影响分析

为了提高汽轮机转子系统中支承轴承的油膜刚度,以三瓦油膜支承可倾瓦轴承为研究对象,研究静压孔相对位置对轴承承载性能的影响规律。建立了油膜支承可倾瓦轴承油膜润滑模型,并运用计算流体动力学方法数值求解三维N-S方程,揭示了不同静压孔相对位置下轴承压力分布、最小膜厚、偏心率、刚度等性能参数的变化规律。分析结果表明：在载荷为890 N的情况下,改变孔的位置可以提高轴承油膜刚度;当静压孔相对位置γ=5°左右时,孔位置接近油膜最大压力分布区,与γ=0°时相比,最小膜厚和偏心率分别减小9.8%和48%,主刚度kyy、kxx接近原结构的1.4倍和1.1倍,此时静压孔位置为相对最优位置区域。依据分析结果开发了新型油膜支承可倾瓦轴承（γ=5°）,通过试验对比分析了普通滑动轴承与新型油膜支承可倾瓦轴承的综合性能,结果表明,高转速时所开发的新型油膜支承可倾瓦轴承具有更好的承载性能与减振性能。研究结果对油膜支承可倾瓦轴承的性能分析具有一定的参考价值,设计轴承静压孔时可根据油膜压力分布规律对其优化以提高轴承性能。     

支点弹性、阻尼可倾瓦轴承动力特性数值仿真及试验研究

依据考虑瓦块摆动和沿几何预载荷方向微幅振动的可倾瓦轴承完全动力特性的解析模型及其对应的八参数简化动力模型,设计制备了支点弹性、阻尼特性可倾瓦轴承。该轴承通过在瓦块支点与轴承体之间设置弹性垫片,使瓦块支点支撑在弹性垫片上,弹性垫片与轴承体之间存在微小间隙并与轴颈润滑系统共享油路以实现局部挤压油膜效应。根据不同加工工艺,制备了两种形式的新型支点弹性、阻尼轴承,并通过理论计算模拟与试验分析对两种新型轴承的动力特性进行研究。结果表明,支点弹性、阻尼可倾瓦轴承能够增大转子的一临界阻尼,有效提高转子系统稳定性。     

Characteristics of a hybrid journal bearing with one recess: Part 2: Thermal analysis

A thermal analysis is made of a fluid-film hybrid journal bearing with one recess under steady-state and adiabatic conditions. The coupled Reynolds equation and energy equation are solved simultaneously by a finite difference method with a successive under-relaxation method. The results for isothermal conditions with effective temperature and feed oil temperature are also obtained for comparison. The load capacity for the adiabatic condition is lower than that for the isothermal condition due to temperature gradients as well as the higher temperature distribution in the high pressure zone. Moreover, the high pressure recess works as a cooling source, so that the maximum temperature occurs at the edges of the bearing and near the position of minimum film thickness. The side flow decreases as the eccentricity increases in the adiabatic condition. This is caused by the rapid decrease in film thickness when eccentricity increases, which dominates the effect of pressure-induced flow.