透平式能量回收一体机水润滑转子稳定性研究

为了保障膜法海水淡化系统中透平式能量回收一体机的稳定运行,对一体机水润滑转子的稳定性展开研究。基于流体动压滑动轴承理论,同时考虑水润滑轴承和口环间隙水膜的流体动压润滑效应,在MATLAB平台上利用有限差分法、扰动增量法求解雷诺方程,得到水润滑滑动轴承及口环的动力特性系数,并对水润滑转子系统的动力学特征方程进行求解,进而判别转子系统的稳定性,研究了临界状态下系统转速与质量的关系。结果表明：口环间隙水膜的承载力在转子稳定性分析中不可忽略,否则将产生较大误差;考虑口环产生的动压润滑效应后,滑动轴承处水膜压力约减小40%,系统动力特性系数增加,系统的临界转速相较仅考虑滑动轴承时提升了3 000 r/min,临界质量提升了8.4%;滑动轴承的主刚度系数与交叉阻尼系数受转速的影响明显高于口环处。研究结果为提高海水淡化一体机水润滑转子系统的可靠性提供了参考。     

滑动轴承可靠性电算程序

本文按液体动压润滑理论,在液体动压滑动轴承设计基础上,为了确保滑动轴承在液体动压润滑状态下工作具有足够的可靠性,考虑到由于制造误差和工作条件的不稳定,使一些参数为随机变量,并视为正态分布规律。液体动压润滑状态的设计准则是H_1-K_1≥0。H为油膜厚度,K_1为表面粗糙度等组成的总厚度。取H与K_1为正态随机变量函数。根据干涉理论,求得液体动压润滑状态的可靠度。     

汽轮发电机径向滑动轴承性能研究

基于流体动压润滑理论,计入温粘关系和紊流效应,对汽轮发电机滑动轴承性能进行了理论研究。针对汽轮发电机滑动轴承结构,开发了适于工程应用的多种汽轮发电机用轴承性能计算程序。对汽轮发电机径向滑动轴承进行了计算,分析了轴承静动特性和稳定性参数,并验证了计算结果的可靠性。     

不同结构参数对水润滑滑动轴承动压效应的影响

水润滑滑动轴承在水液压柱塞泵/马达、潜水电机等海洋水下机械装备中应用广泛,其性能好坏对整机可靠性具有重要影响。对水润滑滑动轴承动压效应进行了理论分析,基于Reynolds方程建立了轴承动压效应的数学模型并通过有限差分法进行数值求解,系统分析了偏心率、半径间隙、宽径比等不同结构参数对轴承水膜压力分布、偏位角以及承载力的影响规律。仿真结果表明:水膜最大动压值及承载力随偏心率的增加而增大,偏位角则随偏心率的增加而减小;半径间隙的增大会使轴承承载力近似呈线性减小;增大宽径比有助于提高水膜动压承载能力,但承压增幅将不断减小。为水润滑滑动轴承的设计选型以及高可靠水液压元件、潜水电机等水下机械装备的研制提供参考。     

动压轴承的噪声和振动分析及控制

本文对流体动压向心滑动轴承的噪声和振动进行分析，提出降低、消除噪声的方法。     

考虑不同加速工况的滑动轴承的启停性能分析*

滑动轴承的摩擦磨损主要发生在启停阶段。为了研究启停工况下的滑动轴承的摩擦学性能,建立一种面向径向滑动轴承的混合润滑数值分析模型。采用质量守恒边界条件的雷诺方程求解流体压力,采用Greenwood和Tripp接触模型预测固体表面接触,而通过Johnson载荷分配概念将润滑模型和接触模型联系起来,从而实现对滑动轴承在启停工况下从混合润滑过渡到动压润滑的摩擦学行为分析。利用该模型,研究轴承系统在启停阶段从边界润滑、混合润滑到动压润滑演化过程中的摩擦学性能;以径向滑动轴承系统为例,结合不同的轴承转速变化函数,分析轴承加速对轴承启停性能的影响;同时研究工作工况、润滑油温度、轴承的结构参数对轴承启停性能的影响。结果表明：轴承启动加速度在合理范围内越大越好,能使轴承更快进入动压润滑;较高的转速、较低的润滑油温度和较大的径向轴承间隙能使轴承拥有更好的启停性能。     

基于CFX的柱面弧形油楔推力滑动轴承仿真分析

柱面弧形油楔推力滑动轴承是一种能够实现双向动载润滑的推力轴承。文中利用Workbench的CFX模块,对柱面弧形油楔推力滑动轴承在动压润滑条件下的油膜特性进行仿真分析。并研究了不同转速和不同黏度对油膜压力的影响,结果表明,转速越高,油膜黏度越大,柱面弧形油楔推力滑动轴承的动压承载能力就越高。     

织构分布对动压滑动轴承油膜压力的影响

以动压滑动轴承为研究对象,根据流体动压润滑原理,建立圆形微凹坑织构化动压滑动轴承油膜数学模型,推导织构化滑动轴承油膜厚度修正公式;结合Reynolds方程有限差分法的求解方法,分析全织构和织构化参数(间距、深度)对动压滑动轴承圆周方向压力分布的影响。结果表明:分布在轴承上的全织构会引起油膜压力的变化;织构位于不同的位置时对圆形微凹坑织构滑动轴承的油膜压力的影响是不同的,对于不同间距和深度的织构,当织构位于升压区时,动压滑动轴承具有较好的润滑、承载性能,而织构位于降压区和全织构时不利于轴承承载。     

油水混合对径向滑动轴承润滑性能的影响

基于流体动压润滑基础理论,利用数值计算方法,在MATLAB软件中建立径向滑动轴承油水混合动压润滑的数学模型,对比分析润滑油中不同含水量对径向滑动轴承润滑性能的影响。结果表明:润滑油中混入少量的水对滑动轴承液膜的厚度和压力产生了一定的影响,最小液膜厚度随含水量的增加而减小,最大液膜压力随含水量的增加而增加;润滑油中混入少量水使得液膜合力和摩擦力变大,将不利于轴承的动压润滑,从而导致轴承润滑性能变差,并且加大轴承的摩擦磨损,降低径向滑动轴承的使用寿命。     

不同预负荷对椭圆滑动轴承的静动特性的影响

流体动压径向滑动轴承以润滑油为工作介质实现重载转子的润滑,在重型和大型以及超大型机械中应用广泛。建立椭圆滑动轴承的径向流体动压滑动数值模型,通过Dyrobes软件分析不同预负荷条件下椭圆滑动轴承对油膜刚度与阻尼、油膜压力、Sommerfeld数和雷诺数、摩擦功耗的影响。分析表明适当的增加预负荷能改善润滑条件,第二油楔面的形成有利于增加转子的稳定性。上述分析结果对椭圆滑动轴承的设计提供了设计参考依据。     

On Performance Characteristics of Three-Lobe Porous Hydrodynamic Journal Bearings

This paper presents an analysis of a three-lobe porous hydrodynamic journal bearing for its static and dynamic performance characteristics. The performance characteristics of the bearing have been computed and presented in graphical form for a wide range of permeability parameter to investigate the effect of porosity on bearing performance. The stability margin of the three-lobe journal bearing system, in terms of crtical mass of journal, has been established using Routh's criteria. The nature of transient motion of the journal has been analyzed using the complex eigen values of characteristic equation and motion trajectories obtained by numerical integration of equations of motion.     

Nonlinear dynamic response of cable-suspended systems under swinging and heaving motion

In order to enhance the fidelity, convenient and flexibility of swinging motion, the structure of incompletely restrained cablesuspended system controlled by two drums was proposed, and the dynamic response of the system under swinging and heaving motion were investigated in this paper. The cables are spatially discretized using the assumed modes method and the system equations of motion are derived by Lagrange equations of the first kind. Based on geometric boundary conditions and linear complementary theory, the differential algebraic equations are transformed to a set of classical difference equations. Nonlinear dynamic behavior occurs under certain range of rotational velocity and frequency. The results show that asynchronous motion of suspension platform is easily caused imbalance for cable tension. Dynamic response of different swing frequencies were obtained via power frequency analysis, which could be used in the selection of the working frequency of the swing motion. The work will contribute to a better understanding of the swing frequency, cable tension and posture with dynamic characteristics of unilateral geometric and kinematic constraints in this system, and it is also useful to investigate the accuracy and reliability of instruments in future.     

A novel dynamic model for multiple configurations of machine tools using a coordinate transformation method

Virtual machine tools have been used widely for simulating designs in computer environments to determine optimal design parameters without the need for manufacturing prototypes. Machine tools include different multiple configurations that are designed to be suitable for the differing requirements of production. To date, studies on dynamic analysis have been limited to a few-axis machine tools of a specific configuration, such as a 3-axis milling machine or a 4-axis grinding machine. Here, we propose a novel method to focus on the dynamic analyses of multi-axis machines with differing multiple configurations. The motion equations for multiple degrees of freedom of linear and rotary axes are established by a Lagrange energy method, equilibrium equations, and Newton’s second law. This technique formulates the motion equations for each axis, and then further develops them for a multi-axis machine through a combination process and a transformation matrix. The library includes five dynamic model components, built to simulate 1236 different configurations of a machine tool. A dynamic analysis was applied to a control system to simulate the control signals of a virtual machine, which include stepped, ramped, curved, sinusoidal, and circular responses, and frequency response functions. The simulated and experimental results demonstrated that the method has high accuracy and reliability for one-, two-, and four-axis machine tools. Thus, this method can simulate the dynamic analyses of multi-axis machines and different multi-configurations without the need to build a specific configuration for each machine. It is recommended for selecting optimal motors, design parameters, and control parameters of the multiple configurations in a machine tool.     

大间隙环流中轴承支承的单质量转子系统特征值分析

建立了大间隙环流中动压滑动轴承支承的单质量转子系统运动方程和特征方程，分析了系统参数对特征值的影响。结果表明，动压滑动轴承特性系数（如刚度和阻尼系数）、大间隙环流特性参数（如流体动力质量、壁面摩擦因数和无量纲间隙比）以及单质量转子系统参数（如系统固有频率）对系统特征值有不同程度的影响。结果表明：随着表征轴承刚度特性的ω1的增大，失稳转速增加，最终γ趋近于2，即相当于Jeffcott转子系统，同时临界转速也随之提高；随着表征轴承阻尼特性ζ的增大，失稳转速不变，临界转速提高；随着表征大间隙环流特性的流体动力质量α的增大，失稳转速不变，临界转速下降；随着表征大间隙环流特性的壁面摩擦因数和无量纲间隙比值β的增大，失稳转速和临界转速均不发生变化：随着表征单质量转子特性的固有频率ω0的增大．失稳转速下降．临界转速降低．     

基于非完整约束的轮式足球机器人运动控制

将基于全局视觉的机器人足球系统的坐标系与轮式足球机器人的运动非完整约束相结合,从运动分析出发,推导出运动控制公式,分析动力学约束、赛场物理结构以及主客场位置对运动控制的影响,得到运动控制公式应用的限制条件.试验和比赛表明,根据公式和分析设计出的运动控制算法使得机器人能够沿着一系列的圆弧轨迹准确、平滑、快速地运动到静止的或运动的目标点.     

Stability of tri-taper journal bearings under dynamic load using a non-linear transient method

Stability of a tri-taper journal bearing which is subjected to steady, periodic and variable rotating loads is studied theoretically using a non-linear transient approach. The hydrodynamic forces are initially obtained by solving the Reynolds equation, satisfying the Reynolds boundary conditions. Further, the transient behavior of rotor bearing system is predicted by substituting these hydrodynamic forces in the equations of motion and then solving them by fourth order Runge Kutta method. Stability of the rotor bearing system is determined from the journal locus. Comparative studies predict that the dynamic performance is superior for a bearing with high ramp size and aspect ratio.     

ON THE AXIAL TRANSIENT RESPONSE ANALYSIS OF THE SECTOR-SHAPED HYDRODYNAMIC THRUST BEARING-ROTOR SYSTEM IN A TURBOEXPANDER

NOTATIONS(The letters in brackets denote the dimension to be as 1)C──Damping coefficient of oil filmD──Domain of a thrust pad in the thrust bearingF──Axial external force (static load)ΔF──Increment of axial external forcesFr──Resultant of oil film forcesF1,F2──Oil film forces of thrust bearings 1 and 2ΔFr──Increment of oil film forces resultantk──Stiffness coefficient of oil filmm──Mass of rotorp()──Oil film pressure,=pδ20/μωr21p1(1),p2(2)──Oil film pressu…     

大位移、变拓扑空间机构的动力分析

给出了一种大位移、变拓扑空间机构的动力分析方法。由物体相对坐标和有限元节点坐标描述系统的运动与变形，通过运动相容条件确定系统空间构形的连续性和唯一性，建立了变结构、刚柔多体系统动力学方程。并由算例表明了该方法的精度与效率     

大间隙环流中复杂轴承-转子系统振动特性研究

基于Myklestad传递矩阵法建立了大间隙环流中动压滑动轴承-转子系统的运动方程，用迭代方法确定了轴承．转子系统的静态平衡工作点，采用数值方法分析轴承-转子系统的振动特性。数值计算结果表明：大间隙环流使轴承-转子系统的固有频率、阻尼临界转速和稳定性均发生了不同程度的变化。大间隙环流不仅与轴承．转子系统发生了动态固耦合，而且也发生了静态固耦合。     

机器人工作空间配置的可靠性规划

机器人工作空间是机器人运行控制的一个重要指标。本文依据动作可靠性的基本概念 ,结合机器人动作可靠性评价的基本要求 ,建立了机器人运动误差分析模型。基于针对机器人工作空间配置的数学描述 ,给出了机器人工作空间配置的可靠性评价方法与规划策略。运用一个 4自由度机器人工作空间规划分析的实例说明 ,机器人工作空间配置的可靠性规划 ,是全面完善系统性能的一个有效途径。