滑动轴承动力特性系数动态分析方法

采用滑动轴承动力特性系数动态分析方法用以研究滑动轴承动力特性系数瞬态响应.分别采用有限元法与有限差分法分析转子瞬态响应与油膜流场压力分布;数值积分油膜压力关于扰动的偏微分项求解滑动轴承动力特性系数;在每个时刻采用学科间迭代方法实现转子响应分析与滑动轴承动力特性系数分析之间的耦合.以某型涡轮增压器转子系统为例,分别采用动态滑动轴承动力特性系数与定滑动轴承动力特性系数分析转子系统瞬态响应;讨论间隙宽度、轴承长度和润滑油粘度对动态滑动轴承动力特性系数的影响,并与文献中的结论进行比对,验证该方法的有效性.     

迷宫密封的气流激振力及其动力特性系数的研究

迷宫密封的气流激振是大型透平机组发生失稳的一个重要原因。评价转子系统稳定性的主要在数之一便是动力特性系数。对迷宫密封的动力特性系数提出了一种新的理论计算方法,理论计算与实验结果之间吻合良好。通过分析各有关参数对动力特性系数的影响,为迷宫密封气流激振的防治提供了对策。     

基于流固耦合的滑动轴承非线性油膜动特性研究

针对采用传统静态滑动轴承动力特性系数分析转子从启动到稳定在平衡位置这段时间内瞬态响应的误差较大的问题,提出了采用有限变分法和Newmark-β法相结合的非线性油膜动特性动态分析方法。该方法首先采用有限变分法计算非线性油膜动力特性系数, 解决了采用有限差分法时多次迭代的时效问题,大大提高了计算效率;然后根据计算得到的非线性油膜动力特性系数,通过Newmark-β法分析转子系统的瞬态响应,用学科间迭代方法实现了非线性油膜动力特性系数与转子瞬态响应之间的流固耦合;最后以Jeffcott转子系统为例,对比研究了传统静态分析方法与动态分析方法。结果证明,采用动态分析方法得到的转子系统瞬态响应幅值更小,精度更高。     

部分锥度密封环对离心泵转子动态特性的影响

根据Hirs理论对湍流工况下部分锥度密封环的动力特性系数及泄漏量进行了数值计算,并具体结合一台双吸泵分析了主要参数变化对密封环动力特性系数、泄漏量以及临界转速的影响,从改善转子动态特性、减小泄漏、提高耐磨性的角度对密封参数的选择提出了建议.     

挤压油膜阻尼器动特性系数的数值解法

在分析含挤压油膜阻尼器转子系统的稳定性和动态响应时,需用到八个油膜动力特性系数。当前常用的动力特性系数的解析表达式是基于长、短轴承近似理论简化得到的,其优点是有明确的解析式且计算量小,缺点是精度较差。基于有限元法计算挤压油膜阻尼器动力特性系数:使用泰勒级数将瞬态雷诺方程的分解,采用伽辽金法将分解后的方程进行变分,然后运用有限元方法求解阻尼器的八个油膜动力特性系数。以某转子-油膜阻尼器系统为对象,分别研究了有限元法数值解和短轴承理论模型近似解对转子动力学特性的影响,并与实验值进行比较,研究结果表明:采用有限元法数值解模拟阻尼器动态特性,较短轴承理论近似解更接近于实验值。     

密封动力特性系数试验识别方法及影响因素分析

引入转子动力学双平面平衡理论,将多级密封内的分布气流力等效到气缸两个端面上,建立多级密封动力特性系数识别模型.该模型考虑气缸平动和偏摆混合运动情况,并通过共振的方法放大气流力影响,从而提高识别精度.构建密封动力特性试验台,研究进出口压比、转速、偏心、间隙等因素对密封动力特性系数的影响.试验结果表明,8个刚度阻尼系数随着进出口压比增大有明显增大,且垂直和水平方向存在耦合效应.随转速增大,交叉耦合刚度系数和直接阻尼系数随转速变大趋势明显,而直接刚度系数和交叉阻尼系数变化不很明显.偏心状态下的交叉耦合刚度系数比同心状态下变大,而直接阻尼系数则减小,说明转子在偏心状态下比同心状态下更容易失稳.随密封平均间隙变小,8个动力特性系数绝对值增大.     

分数阶微分型黏弹性地基上变厚度矩形板的动力响应分析

研究了黏弹性地基上变厚度矩形薄板的动力响应。采用分数阶微分的Kelvin-voigt模型描述地基的黏弹性特征,基于弹性板的基本假设,对于小变形问题,建立了黏弹性地基上变厚度矩形薄板的动力控制微分方程。针对该分数阶变系数偏微分方程,采用Galerkin法和Haar小波配点法进行数值求解。分析了四边简支板的动力响应特性,得到了均布载荷作用下线性模型、抛物线模型板中心挠度曲线,讨论了变厚度矩形板的厚度比、长宽比、分数阶导数的阶数、地基弹簧系数、粘滞系数、水平剪切系数等参数变化对板动力特性的影响。     

链传动的运动学实质及动力特性改善

本文借助连杆机构运动学的方法探讨链传动的运动学实质,定义并研究了链传动的变节位置,给出并讨论了评定链传动动力特性的若干系数,提出并验证了微调中心距以改善动力特性的方法及效果。     

部分锥度环状间隙短密封动力特性计算分析

根据Hirs湍流润滑理论提出了一种计算部分锥度环状间隙短密封压力场及动力特性系数的方法。密封中的周向流动和轴向流动均假设为湍流状态。对Hirs湍流润滑方程的求解采用摄动法 ,由相应的零阶近似方程可求得稳态周向速度分布 ,压力分布及密封泄漏量 ;对短密封作类似于计算短轴承的处理 ,使一阶近似方程得到适当简化 ,方程的解给出扰动压力的表达式 ,对其进行数值积分便可确定各个动力系数。针对计算中出现的锥度变化处未知量对轴向坐标导数不连续问题提出了相应的解决措施。计算结果与现有实验结果比较一致。通过实例计算分析了全锥度密封在不同磨损程度下动力特性系数的变化情况 ,并将部分锥度密封动力特性系数与平密封以及全锥度密封进行了分析比较     

旋转式换向阀的动态响应特性及稳定性分析

为了实现电液激振系统的高频振动，提出一种旋转式换向阀。推导了旋转换向阀的动力学方程并通过MATLAB对旋转换向阀的动态响应特性进行数值求解，分析了阻尼系数、转动惯量、液动力矩对旋转换向阀动态响应特性及稳定性的影响规律。研究结果表明：阻尼系数、转动惯量、液动力矩对旋转换向阀的响应速度、稳定性及工作带宽均有较大影响，其中液动力矩对旋转换向阀的影响程度最强，阻尼系数对旋转换向阀的影响程度最弱。研究结果可为提高旋转换向阀的动态响应特性及稳定性提供数据支撑和优化导向。     

Novel approach to solve the dynamical porous journal bearing problem

Analytical pressure solutions are a simple and robust way to model plain journal bearings in rotordynamics, but cannot be extended to porous journal bearings. Using the method of weighted residuals—viz. Galerkin's method with global shape functions—a novel and fast approach to solve the dynamical porous journal bearing problem is proposed. This approach allows for the influence of rough surfaces on the hydrodynamic pressure implemented through flow-factors, journal misalignment and calculation of stiffness and damping coefficients for finite bearings. The proposed method will be verified using analytical expressions and new results will be shown for porous journal bearings including the influence of rough surfaces.     

Stiffness and damping coefficients for journal bearing using the 3D transient flow calculation

The dynamic coefficients of journal bearing are necessary components in the analysis of linear stability and response of rotating dynamic systems. We propose a new method for the numerical identification of bearing support force coefficients in flexible rotor-bearing systems based on the 3D transient flow calculation. The CFD commercial software FLUENT is mainly used in this simulation, which employs a finite volume method for the discretization of the Navier-Stokes equations. To determine the dynamic coefficients, a new mesh movement approach is presented to update the volume mesh when the journal moves during the 3D transient flow calculation of a journal bearing. Existing dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. Measurements and identification are performed on a test rotor supported on a pair of identical two-lobe fluid film bearings, and the results obtained from the CFD methods agree well with experimental results. The results indicate that the methods proposed in this paper can predict the dynamic coefficients of the journal bearing in a rotor-bearing system effectively, and provide a further tool for stability analysis.     

A new approach to flow through a region bounded by two ellipses of the same ellipticity

A new method, called the “force assembly method”, for the numerical calculation of the dynamic coefficients of tilting-pad bearings is proposed. The method is based on a finite element solution of the pressure distribution on the surface and the eight coefficients are determined directly by considering the bearing as a whole; they are not determined from the traditional assembly of modified fixed-pad data. Some important advantages in theoretical consistency are found without any increase in computational difficulty.     

基于气穴模型的动压轴承动态油膜刚度计算方法

针对雷诺方程很难准确反映动压轴承高速转动过程中引起的周向惯性效应、动态挤压效应等的影响,进而导致油膜动态刚度计算精度难以满足高精度轴承设计的现状,提出用ADINA软件先求解瞬态油膜压力分布和瞬态油膜力,得到轴心轨迹,然后结合差分计算模型计算油膜动态刚度的方法。该计算方法基于流固耦合和气穴模型,定义油膜和轴的流固耦合时,采用任意的拉格朗日-欧拉(ALE)算法有效避免了油膜网格畸变的问题,再现轴心动态平衡过程和三维流场压力分布的动态发展过程,得到瞬态过程中的动态油膜力和动态油膜刚度。试验结果和基于流固耦合和气穴模型的计算结果对比分析发现两者基本吻合,说明该基于流固耦合和气穴模型的数值仿真计算方法是可行和有效的。     

Eccentricity and Misalignment Effects on the Performance of High-Pressure Annular Seals

Annular pressure seals act as powerful hydrostatic bearings and influence the dynamic characteristics of rotating machinery. This work, using the existing concentric seal theories, provides a simple approximate method for calculation of both seal leakage and the dynamic coefficients for short seals with large eccentricity and/or misalignment of the shaft. Rotation and surface roughness effects are included for leakage and dynamic force calculation. The leakage calculations for both laminar and turbulent flow are compared with experimental results. The dynamic coefficients are compared with analytical results. Excellent agreement between the present work and published results have been observed up to the eccentricity ratio of 0.8.     

ISO/TC 4关节轴承额定载荷标准的发展

介绍了ISO/TC 4关节轴承额定载荷标准制定过程,并叙述了关节轴承额定载荷的计算方法标准发展历程:1997年首次制定了国内关节轴承额定载荷计算方法和寿命估计方法的行业标准,2010年国内有关单位联合对该标准进行了修订,2013年全国滚动轴承标准化技术委员会将国内关节轴承额定载荷和寿命估计标准提交到ISO/TC 4。经过多年的研究,ISO/TC 4/SC 8发布了ISO 20015:2017和ISO/TR 20051:2020两项有关关节轴承额定载荷计算方法的国际标准,并对其主要内容进行了介绍。     

Experimental determination of the stiffness and damping coefficients of fluid film bearings by means of step forces

A method of identifying bearing dynamic coefficients by means of step forces is described. Obtaining an accurate fast Fourier transform of the rapidly varying step function is difficult since the limitations of real time analysis by minicomputer make truncation necessary. This paper therefore proposes a feasible approach to direct analysis of the spectrum of the step function and introduces its application to measure the stiffness and damping coefficients of journal bearings. The approach followed is to use a step exciting force on the test bearings. By using the proposed direct spectrum analysis method, the transfer functions of the bearing systems and eventually the dynamic coefficients of the journal bearings can be derived.     

Boundary conditions for the calculation of the dynamic characteristics of infinitely long journal bearings with turbulence and inertia effects

A discussion is presented concerning the various pressure boundary conditions used in the calculation of the dynamic characteristics of infinitely long journal bearings under turbulent operating conditions including inertia effects. The dynamic characteristics of bearings such as the spring, damping and acceleration coefficients and the stability limit curves of a rigid rotor supported by two identical symmetrically aligned bearings are determined with four kinds of pressure boundary conditions. The calculated results for each condition are indicated in graphical form. It is concluded that the pressure boundary condition plays an important role in determining the dynamic characteristics when turbulent and inertia effects are included.     

滚动轴承寿命计算中当量动载荷的确定

滚动轴承的寿命是衡量滚动轴承承载能力的重要指标。滚动轴承寿命计算的核心问题是当量动载荷的计算,而对不同类型的轴承当量动载荷计算的方法也不同。介绍了滚动轴承当量动载荷计算的一般过程和难点。