混合轴承动特性简化计算方法

用一维流计算原理分析了多腔混合轴承的动态特性；计算了典型的毛细管节流四腔轴承在各种设计参数下的线性化刚度系数和阻尼系数，得到了轴承相应的刚度和稳定性速度阈值；比较了简化计算方法得到的数据与传统的雷诺方程数值解法得到的数据，且讨论了前者的误差影响。在常用工况条件下，其计算结果满足工程需要。     

磁气负载比对箔片-磁力混合轴承支承特性及转子动力学特性的影响

箔片-磁力混合轴承是一种能降低箔片轴承起飞前的摩擦损耗且可改善磁轴承高速时的承载和动力学性能的新型高性能主动控制型轴承。提出了一种箔片-磁力混合轴承的设计方法,设计并搭建箔片-磁力混合轴承支承特性实验台和箔片-磁力混合轴承转子实验台,实验探究了磁气负载比(即气体箔片轴承和主动磁轴承之间的载荷分配比)对箔片-磁力混合轴承支承特性和转子动力学特性的影响。实验结果表明：箔片-磁力混合轴承比箔片轴承的总体静态刚度和刚度变化率有所提高。箔片-磁力混合轴承结构刚度随频率的提高而增大,等效黏性阻尼随频率的提高呈现先降后增的趋势。此外,合适的负载比可以降低起飞转速,改善摩擦损耗,抑制次频振,有利于提高转子的高速稳定性。     

可倾瓦阻尼轴承的开发和应用

为了提高压缩机转子稳定性,降低转子振动和缓解气体激振等情况的发生,在可倾瓦轴承的基础上,研究开发了可倾瓦阻尼轴承;建立了阻尼器的流固耦合力学模型,计算出瓦块支点的刚度、阻尼系数,进而得到可倾瓦阻尼轴承的总刚度和总阻尼系数,并分析转子稳定性,最后通过在产品中的实际应用,验证了可倾瓦阻尼轴承的特性,为可倾瓦阻尼轴承的设计、产品稳定性的提高提供了理论支持与实践经验。     

考虑边界滑移状态的液体动静压球轴承稳定性分析

液体动静压球轴承稳定性分析包括探究其动态特性及临界转速,其刚度和阻尼系数对轴承转子系统稳定性具有重要影响,而研究临界转速可有效避免轴承转子系统发生涡动失稳。考虑边界滑移条件,将小孔节流器进入油腔流量与封油边流出流量相等作为边界条件,求解出边界滑移状态下的Reynolds方程得到油腔压力和封油边压力;对边界滑移状态下瞬态Reynolds方程采用小扰动法推导出扰动压力偏微分方程,结合有限差分法和松弛迭代法求解方程得到边界滑移状态下液体动静压球轴承的刚度和阻尼系数,进而通过线性稳定性方法求解临界失稳转速,探讨滑移系数、供油压力、转子转速之于轴承动态特性的影响及临界转速之于滑移系数的变化规律。结果表明,滑移系数增大会导致4个刚度系数和交叉阻尼系数减小、直接阻尼增大;供油压力增大将导致8个动态特性系数均增大,转速增大将导致刚度增大及阻尼减小,且滑移效应的发生不影响上述规律;临界转速随滑移系数的增大而减小,系统稳定性降低。     

基于结构动态特性的磁力轴承转子系统的设计

分析了径向磁力轴承动力学特性,计算了磁力轴承的刚度系数和阻尼系数。在此基础上,对磁力轴承的转子结构动态特性进行了有限元分析。提出了基于结构动态特性的磁力轴承转子控制系统的设计方法。     

轴承抗汽流涡动系数的计算

针对超超临界汽轮发电机组稳定性问题,计算了某高压转子轴承稳定性系数,研究了轴承稳定对转子稳定性的影响.     

高速涡轮泵动静压轴承两相润滑特性与稳定性试验研究

通过对气液两相润滑下轴承静动特性、轴承稳定性以及两相润滑特性及稳定性的试验研究,建立基于理论与试验混合建模的轴承静动特性分析方法,解决了理论分析时采用混合均质模型得到的方程不封闭的问题;提出高速低温动静压轴承支撑转子系统的稳定性综合试验技术,实现了从多角度试验研究轴承稳定性问题,各子项测试结果可互相辅佐和验证,解决了传统稳定性测试技术中试验结果孤立的问题;揭示两相润滑下轴承的重要性能规律:汽化使刚度增加、稳定性改善,但该效应对参数敏感,使轴承性能不易控制。     

混流式水轮机水导轴承动力特性参数优化设计

对于复杂的混流式水轮机组系统,水导轴承油膜刚度系数及阻尼系数发生变化时,转子的临界转速、不平衡响应也不同。由于精确计算考虑的因素较多,系统的刚度及质量矩阵求解难度较大,所以用解析法求解在工程运用上并不实用。通过采用虚拟样机优化设计技术以转子-轴承系统稳定性为优化目标,利用虚拟样机参数化方法,可以快速简便的对轴承油膜的刚度系数进行优化,为混流式水轮机转子-轴承系统设计与制造提供有效方便的一种新方法。     

基于轨迹法的气体箔片轴承动态特性系数辨识

气体箔片轴承的动态特性系数(动态刚度系数和动态阻尼系数)是该类轴承支承转子系统的瞬态动力学计算和稳定性分析的重要参数,针对传统基于摄动法的动态特性系数计算仅考虑单个涡动比,提出基于轨迹法的动态特性系数辨识方法,对转子施加简谐激励,联立气膜雷诺方程和转子运动方程得到转子的轴心轨迹,采用线性简谐激振法和简谐激振法辨识出轴承的动态特性系数。以某气体箔片轴承为例,采用线性简谐激振法、简谐激振法对其动态特性系数进行计算,计算结果与摄动法均存在一定的差距,但对于气体箔片轴承在可接受范围之内。     

基于流体域仿真的高速风机气浮箔片轴承动静特性研究

气浮轴承特性对高速风机转子稳定性有显著影响,气浮轴承的静特性与动特性计算是准确获得转子系统失稳转速的基础。通过建立气浮轴承物理模型,以及对应的流体域模型,设定气浮轴承工作状况下的参数,模拟其在工作状况下的流体域分布情况,调整轴心位置,找到标准工作状况下的轴心位置,实现气浮轴承的静特性计算。在静特性计算的结果的基础上,赋予轴颈同频的扰动,模拟流体域分布情况,得到在给定扰动情况下轴颈的受力情况,根据力的变化求解得到气浮轴承对应的刚度系数与阻尼系数,实现气浮轴承动特性的计算。结果表明：随着转速的不断提升,稳定时的轴心位置会逐渐向气浮箔片轴承的圆心靠近;在一定的工作转速范围内,轴承的直接刚度系数随着转速的提升而下降,直接阻尼系数则在工作转速范围内下降到达低值后上升。分析气浮轴承的特性系数与转速之间的变化规律,可为开展转子系统动力学研究提供理论基础。     

On the non-linear stability of self-acting gas journal bearings

The non-linear stability of finite length self-acting gas journal bearings is studied by solving a time-dependent Reynolds equation using finite difference method. Two threshold values are discovered instead of one through which the self-acting gas journal bearings are changed from stable to unstable state. Keeping other parameters unchanged, when the mass of rotor exceeds the upper threshold value of mass, the system gets unstable; when the mass is less than the lower threshold value of mass, the system is stable; when the mass is between these two threshold values, the stability of bearings is determined by the amplitude of disturbance. Similar facts of two threshold values are also found when the stability parameter is chosen as external force or aspect ratio.     

精密离心机静压气体轴承主轴系统的稳定性分析

惯性导航用精密离心机静压气体轴承主轴系统的运动稳定性是保障其标定加速度计精度的重要前提，直接关系到整个机组的安全性与可靠性。将静压气体轴承等效为弹性支承，使轴承的刚度以显函数出现，对主轴的稳定性进行了分析，确定了轴系运动的稳定性条件。通过数值仿真，得到了稳定性区域。分析了转速、支承刚度和转动惯量对轴系运动稳定性的影响，为提高精密离心机的性能提供了一定的依据。     

Linear Stability Analysis of a Rough Short Journal Bearing Lubricated with Non-Newtonian Fluids

On the basis of Stokes theory and the Christensen's stochastic model, the combined effects of couple stresses and surface roughness on the instability threshold of hydrodynamic rotor bearings are theoretically studied. The film pressure is solved from the generalized stochastic non-Newtonian Reynolds-type equation and applied to evaluate the equilibrium solution of a short journal bearing. By using the linear theory, the eight oil-film stiffness and damping coefficients as well as the vibrational stability boundary were determined. According to the results obtained, the presence of couple stresses accompanied with a longitudinal roughness provides an increase in the values of stiffness coefficientsK _XX , K _XY and K _YX as well as the damping coefficient C _XX , and results in a higher stability threshold speed. Whereas, when compared to the smooth bearing lubricated with couple stress fluid, a decrease in the threshold speed is found in the case of transverse roughness.     

The restrictive effects of capillary compensation on the stability of the Jeffcott rotor-hybrid bearing system

The influence of restriction parameters, recess depth and land-width ratios on the load capacity and stability of a Jeffcott rotor supported by single-row, six-recessed hybrid bearings with capillary compensation is studied. The finite difference method is used to solve Reynolds equation, whilst the determination of stability threshold uses the Routh-Hurwitz method. The load capacity, stability threshold, and the critical whirl ratio, versus the changing restriction parameters, are each simulated for both shallow-recessed and the deep-recessed bearings with various land-width ratios. Simulated results indicate that small land sizes are necessary for shallow-recessed bearings in order to yield good performance, and these bearings are superior to deep-recessed bearings. Furthermore, both load capacity and stability threshold become correspondingly greater with a decrease in the restriction parameters. Nevertheless, the appropriate design of both restrictor and land size in deep-recessed bearings might well induce both load capacity and stability threshold greater than in shallow-recessed bearings.     

齿轮-转子系统的振动特性分析

根据转子动力学和齿轮啮合的基本原理,建立了考虑陀螺力矩的齿轮转子系统的动力学模型,以此求得齿轮转子啮合刚度矩阵和阻尼矩阵。探讨了啮合刚度、支承刚度对系统固有频率以及系统稳定性的影响。结果表明齿轮的啮合刚度对弯曲振动以及弯扭耦合振动固有频率的影响不大,而当啮合刚度介于2×105~2×108之间时,对弯扭耦合振动的相对稳定性却有较大的影响;另增大支承刚度,固有频率相应提高;减小跨距可以提高系统的稳定性。分析结果对工程应用具有重要的意义。     

Dynamic stability experiments of compliant foil thrust bearing with viscoelastic support

In order to reduce the complexity of machine construction and improve the mechanical efficiency, high speed rotation machineries usually implement self-acting gas bearings to substitute the traditional oil-lubricated bearings. This paper presents test results of a gas thrust bearing with viscoelastic support which is designed for high speed turbo-machinery. The gas bearing, which belongs to compliant foil bearings, consists of a top thin metal foil and a bottom thin rubber foil. Static and stability experiments are conducted on a high speed gas turbine test rig. The static results indicate that the structural stiffness of test bearing generally increases with the increase in axial load and the decrease in thickness of bottom foil. In the rotation tests, rotor runs stably with small vibration amplitude, which is dominant in waterfall plot during whole speed up procedure. It shows that test bearing has preferable stability characteristics for high speed gas turbines.     

Stability Analysis on Rotor Systems Supported by Self-acting Tilting-pad Gas Bearings with Frequency Effects

The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation frequencies are same as the rotating speed are used to carry out the stability analysis of rotor systems.This method does not contact the frequency characteristics of dynamic stiffness and damping coefficients of gas bearings with the dynamical behaviors of rotor systems.Furthermore,the effects ...     

动压气体轴承-转子系统稳定性分析

本文建立了普通圆柱型动压气体轴承支承的单盘转子系统模型,写出了系统的运动方程,并引用气体轴承的动力特性数值分析所得到的8个动力特性系数,利用Routh-Hurwitz准则,研究了系统的稳定性,计算表明所设计的轴承-转子系统在设计转速范围内的运转是稳定的。讨论了气体轴承结构参数偏心率,长径比及平均径向间隙对稳定性的影响,得出了应当采用小偏心率,小长径比,大平均径向间隙提高轴承转子系统稳定性的结论。     

Dynamic characteristics and stability of a journal bearing in a non-laminar lubrication regime

A mathematical model to determine the stiffness and damping coefficients and the stability limit curves of a journal bearing in a non-laminar lubrication regime is described. The results show the flow regime influence on the dynamic characteristics of cylindrical bearings and on the stability of a rigid rotor on rigid supports.