内外膜独立供油向心浮环轴承稳定性研究

用有限元法计算内外膜独立供油的高速径向浮环动静压轴承的刚度系数和阻尼系数,用Routh-Hurwitz准则给出计入轴颈和浮环质量的稳定性判据。分析供油压力对浮环轴承内外膜无量纲临界质量的影响,结果表明动静压浮环轴承小偏心工作时,降低供油压力可提高系统稳定性;大偏心下工作时,采用较高的供油压力可提高系统的稳定性。     

基于动网格模型的液体动静压轴承刚度阻尼计算方法

针对雷诺方程不能反映高速油流周向惯性效应、轴颈周向动压效应和静压扩散效应之间的非线性耦合关系及其对三维流场特性的影响,进而导致动静压轴承刚度阻尼的计算精度难以满足高转速精密轴承设计需要之现状,提出基于纳维-斯托克斯方程的动网格计算轴承刚度阻尼新方法。该方法采用自定义程序实现轴颈的旋转速度、位移扰动和速度扰动以及扰动过程中油膜力的计算等功能,成功将轴颈的旋转动边界转换为静边界,有效避免因轴颈旋转引起的网格畸变,并利用弹簧光顺模型更新轴颈受速度扰动和位移扰动引起的油膜网格挤压变形。通过对比研究瞬态和稳态条件下油膜力的变化,界定计算刚度阻尼系数时速度扰动和位移扰动的合理取值范围。利用所提出的方法计算典型轴承的刚度阻尼系数,再现动静压轴承油膜厚度和三维流场压力分布的动态发展过程,并采用影响系数法对该轴承的刚度系数进行试验测试。通过对比试验数据和动网格计算结果发现两者基本吻合,表明所提出的计算方法是有效可行的。     

基于MATLAB/GUI的滑动轴承特性研究

以三油楔固定瓦滑动轴承为研究对象,根据定常和非定常雷诺方程,采用有限差分法分别计算了轴承的油膜压力分布和扰动油膜压力分布,进而计算出轴承的静、动特性。采用MATLAB软件自带的图形用户界面的设计功能,实现了轴承特性计算的可视化交互。     

计入气穴影响的径推联合动静压浮环轴承稳定性研究

研究了计入气穴影响的径推联合动静压浮环轴承的动态性能和稳定性.给出了控制径推联合浮环动静压轴承内、外膜的气油两相流变密度、变黏度无量纲动态Reynolds方程及压力边界条件和深腔流量平衡方程;用有限元法对不同转速、不同偏心率下含气率为0和0.1的内外油膜进行了有限元计算,得到各部分的刚度系数和阻尼系数;计算了该径推浮环轴承的稳定性参数.结果表明:气穴使得径向、推力内外层油膜的刚度系数和阻尼系数均有所下降,随着偏心率的增大及转速的提高,气穴的影响程度减小;气穴使得轴承的无量纲临界转子质量降低,因此在供油压力急剧变化时必须考虑气穴的影响.     

基于CFD方法的液体动压滑动轴承动特性研究

应用 CFD 工具 Fluent 建立了滑动轴承压力求解分析模型,计算分析了普通圆柱轴承的压力分布和上、下瓦开槽对滑动轴承压力分布、承载和进油量等因素的影响.比较了 CFD 方法和 Reynold 方程计算结果的差别.结果表明:CFD 方法和 Reynold 方程计算结果基本相同,CFD 方法可以直接求解 N-S 方程,可以更准确地反映轴承动特性.下瓦开槽对进油量的影响不大,但会提高承压区最大压力,从而提高轴承稳定性;上瓦开槽对油膜压力的影响不大,但会导致进油量增加,更好地冷却轴颈.     

球面螺旋槽动静压气体轴承动态特性分析

以半球螺旋槽动静压气体轴承为研究对象,建立球面动静压混合气体轴承的非线性动态润滑计算分析数学模型,采用偏导数法推导出扰动压力控制方程;在广义坐标系下,采用有限差分法对扰动压力控制方程离散化,推导出扰动压力的差分表达式;推导出半球螺旋槽动静压气体轴承刚度和阻尼系数与扰动压力之间的关系表达式;采用VC++6.0编制程序,数值计算出三维微气膜的瞬态扰动压力分布、非线性气膜力及动态刚度系数和动态阻尼系数。研究转速、偏心率及供气压力对气膜动态特性系数的影响规律,结果表明:随着转速、偏心率及供气压力的增大,气膜刚度和阻尼系数均有不同程度的变化。     

热效应对高速圆锥动静压轴承静特性的影响

为研究热效应对高速圆锥动静压轴承静特性的影响,建立具有深浅腔结构的圆锥动静压轴承的Reynolds方程、能量方程、深腔流量平衡方程及相关控制方程;采用有限元法和有限差分法对其进行离散,运用正系数法则对能量方程系数及常数项的离散系数进行处理,联立求解得到油膜压力分布与温度分布,计算出高速圆锥动静压轴承的静参数,并分析热效应对高速圆锥动静压轴承静特性的影响。结果表明:热效应使高速圆锥动静压轴承油膜压力减小,且转速越大,压力减幅越大,油膜温升越明显;计入热效应后,润滑油黏度降低,引起高速圆锥动静压轴承偏位角增大,轴向、径向承载力减小,端泄流量增大,摩擦力减小,且转速越高变化越显著。     

考虑激振频率的可倾瓦推力轴承动特性理论与试验研究

为了研究激振频率对可倾瓦推力轴承动特性的影响,提出考虑激振频率的动特性建模方法和试验方法。依据可倾瓦轴承刚度和阻尼定义,将激振频率引入可倾瓦推力轴承动特性计算过程,通过建立轴向扰动下的膜厚方程、雷诺方程及瓦块运动方程,推导出包含激振频率的可倾瓦推力轴承动特性数学模型,计算分析刚度和阻尼随扰动频率(激振频率与主轴转频的比值)、转速及载荷的变化规律;采用脉冲激振法在可倾瓦推力轴承试验台进行动特性试验,得到不同激振频率、转速及载荷条件下刚度、阻尼的试验结果,并和相应的理论计算值进行对比分析。结果表明：当扰动频率较小时,可倾瓦推力轴承刚度随其增加而逐步增大,阻尼随其增加而逐步减小;当扰动频率增加到一定程度后,其刚度和阻尼逐步趋于稳定。此外,转速和载荷对其刚度和阻尼随扰动频率的变化幅度基本无影响。     

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。     

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。     

含间隙曲柄滑块机构运动副动态磨损研究

含间隙曲柄滑块机构中运动副的润滑情况不同于滑动轴承,其相对速度不足以形成动压润滑而处于边界润滑状态下.为了分析此状态下的动态磨损问题,考虑到含间隙运动副边界润滑时轴套的切向弹性变形和切向阻尼,结合考虑间隙运动副碰撞接触的非线性弹簧阻尼模型,提出边界润滑条件下的间隙副接触力模型,进而在此基础上推导出间隙副的动态磨损模型,并对含间隙曲柄滑块机构的运动副动态磨损进行数值分析.计算结果表明副元素间呈现出连续弹性变形现象,在连续变形接触处,动态磨损量较大使磨损加剧,并出现非均匀磨损.     

Effect of Lubricant Non-Newtonian Behavior and Elastic Deformation on the Dynamic Performance of Finite Journal Plastic Bearings

This paper presents a numerical study of the performance of a dynamically loaded finite journal plastic bearing lubricated with a non-Newtonian fluid, taking into account the elastic deformation of the bearing. The non-Newtonian characteristics are adopted in this paper through an equivalent power-law. An expression for a modified Reynolds equation is derived in order to obtain the pressure gradient. Elastic deformation of the bearing surface was estimated in a direction normal to the bearing surface using Boussinesq equations. The film shape was modified accordingly and then iterated with the hydrodynamic pressure distribution in the bearing until a convergent solution was obtained. The Reynolds equation was solved numerically, considering three values of the flow-behavior index (n = 0.6, 1, and 1.2) and a wide range of journal speeds, materials, and clearance ratios. Consequently, the finite perturbation technique was used to determine the eight values of oil film stiffness and damping coefficients. By using the dynamic coefficients, the stability characteristics of the rotor-bearing system and the critical speed were calculated. The results show that increasing the flow-behavior index enhances the rotor-bearing system stability. A considerable destabilizing effect is obtained upon decreasing the elastic deformation coefficient.     

ANALYSIS OF METHOD FOR DETERMINING AZIMUTH OF PRINCIPAL AXIS OF INERTIA BASED ON DYNAMIC BALANCE MEASUREMENT

The dynamic balance quality of a rotating object is an important factor to maintain the stability and accuracy for motion. The azimuth of the principal axis of inertia is a major sign of dynamic balance. A usual method is measuring moment of inertia matrix relative to some base coordinates on a rotary inertia machine so as to calculate the azimuth of principal axis of inertia. By using the measured unbalance results on the two trimmed planes on a vertical hard bearing double-plane dynamic balancing machine, the dimension and direction of couple unbalance can be found. An azimuth angle formula for the principal axis of inertia is derived and is solved by using unbalance quantities. The experiments indicate that method based on dynamic balancing measurement is proved rational and effective and has a fine precision.     

含间隙弹性机构动态特性分析

在含间隙刚性连杆机构动力学分析的基础上,建立了含间隙弹性连杆机构动力学模型,计入刚弹耦合作用及间隙对杆件弹性变形的影响,利用该方法对一弹性四连杆机构进行动力分析,采用较为简洁的迭代求解方法,通过算例讨论了几类机构的副反力,杆件变形的情况,计算结果表明,该方法是正确可行的。     

可倾瓦推力轴承的线性和非线性动特性研究

建立可倾瓦推力轴承中油膜对镜板的作用力和油膜作用下可倾瓦的力矩的准静态线性和非线性动力学模型,并且通过对油膜压力进行二阶泰勒级数展开推导出４０个油膜对镜板的作用力和油膜作用于可倾瓦的力矩的线性和非线性刚度及阻尼系数,为以后进一步研究推力轴承的稳定性和动特性奠定了基础。     

齿轮系统动态传递误差和振动稳定性的数值研究

建立了计及轮齿时变啮合刚度、啮合阻尼、支承刚度和阻尼的齿轮系统扭转-横向振动耦合的3自由度动力学模型。用数值仿真方法,研究了重合度、支承刚度、啮合阻尼和支承阻尼对齿轮动态传递误差和动力稳定性的影响。研究结论对于高速、精密齿轮传动的动力学设计具有积极意义。     

液体静压支承动态特性分析、实验及其应用

本文在考虑油液及其含气体可压缩的基础上,对液体静压支承的动态特性进行了理论分析,求得静压支承系统动态稳定性的判别公式和动刚度公式。通过试验证明了上述理论的正确性,并总结出对静压支承的设计具有参考价值的理论依据。在生产实践中,运用上述理论解决了静压支承动态不稳定问题,从而提高了支承精度。     

动压气体轴承的动态刚度和动态阻尼系数

采用偏导数法求解动压气体润滑Reynolds方程,给出动压气体轴承动态刚度和动态阻尼系数普遍适应的计算方法.进行有限元数值仿真,计算动压气体轴承的动态刚度和动态阻尼系数,并重点研究轴颈扰动频率和不同轴颈扰动频率下的轴承静态载荷及轴承数对这些系数的影响.从理论上解释动压气体轴承的动态刚度和动态阻尼系数与轴颈扰动频率的密切相关性.     

Integrated Numerical Analysis on the Performance of a Hybrid Gas-Lubricated Bearing Utilizing Near-Field Acoustic Levitation

Aerodynamic bearings utilizing near-field acoustic levitation, as a novel hybrid gas-lubricated bearing, can operate with high precision and high rotational speed with low power loss and wear. This article systematically studied the acting mechanisms of aerodynamic and squeeze effects on the static and dynamic characteristics of a hybrid gas-lubricated bearing. The resonance frequencies and mode shapes of the bearing were obtained from a finite element analysis and validated by published experimental measurements. The effects of static elastic deformation, dynamic elastic deformation, and bearing clearance on the load capacity were analyzed. A nonlinear numerical model coupling the air film and the structural vibration was also developed to investigate the stability of the hybrid gas-lubricated bearing. The predicted bearing load capacity shows reasonable agreement with the experimental data. Results show that the bearing using only the aerodynamic effect has a large load capacity but poor stability. By utilizing the squeeze film effect, especially at a proper resonance frequency, the load capacity of the hybrid gas-lubricated bearing can be improved and its stability can also be remarkably promoted.     

Tilt stiffness and damping of externally pressurized porous gas journal bearings

The dynamic behaviour of an externally pressurized porous gas journal bearing is analysed by assuming one-dimensional flow through the porous bushing. A periodic disturbance (angular displacement) about the transverse axis is imposed on the bearing and the resulting dynamic pressure distribution is determined by small perturbations of the Reynolds equation. A finite difference method is used to determine the dynamic pressure. Design data for tilt stiffness and damping as a function of squeeze number, feeding parameter, supply pressure and porosity parameter are calculated numerically using a digital computer and are presented in tables and figures.