单节流孔静压球面气体轴承动态特性的有限元分析

采用分布参数和小参数摄动方法简化动态雷诺润滑方程，推导了用于计算小孔节流方式的单节流孔静压球面气体轴承气膜动态特性的一系列计算公式，并通过动态压力分布方程的有限元求解得到了气膜的动态刚度、动态阻尼曲线以及轴承的稳定工作范围图谱，进而给出了静压气体轴承的稳定性判据．结果表明，小孔节流方式静压气体轴承的稳定性主要取决于节流气腔的容积、供气压力和承载质量．     

加工误差对陀螺电机用动压气体轴承刚度的影响

为了进一步提高精密H型动压气体轴承的刚度性能,着重分析了轴承加工误差对轴承刚度的影响。首先,通过在轴承内部交界处引入压力和流量连续方程,建立可考虑径向、止推轴承相互作用的H型动压气体轴承模型;然后,采用有限单元法进行求解以得到轴承压力分布及刚度等特性;最后,在对模型和计算结果进行实验验证后,对不同加工误差下的轴承刚度进行了研究。分析结果显示,加工误差对轴承刚度影响由强到弱的顺序为轴承间隙、止推板平面度、径向轴承锥度、圆度和止推板垂直度误差,0.2μm的轴承间隙加工误差可使轴承刚度降低20%～25%,而垂直度误差对轴承刚度的影响不大。研究结果为H型动压气体轴承的结构设计和性能提高提供了有益的参考。     

基于连续模型和离散模型的微尺度三维凸台轴承的气体润滑分析

为了考察应用图案化盘片实现超高密度磁存储时磁头/磁盘界面气体润滑设计理论的有效性,本文设计了1种三维凸台轴承构型,分别使用直接模拟蒙特卡罗方法（DSMC）和气体分子薄膜润滑理论（MGL）方法进行了模拟计算,考察了相对滑动速度、轴承最小间隙、凸台高度和入射速度方向对气体轴承压力分布的影响.结果表明：对于三维凸台微尺度气体轴承,MGL方法的计算结果依然与DSMC方法的结果相差不大.存在凸台接触,轴承间隙为零的情况下,气体轴承仍然具有一定的承载能力,且压力分布形状随凸台高度的变化表现出与常规非接触式气体轴承不同的规律.     

局部多孔质气体静压轴向轴承静态特性的数值求解

运用数值方法分析局部多孔质节流气体静压轴向轴承的静态性能,分别建立局部多孔质圆柱塞内的压力分布方程和气体薄膜内的压力分布方程,利用坐标变换将局部多孔质圆柱塞的圆柱坐标与气体薄膜的圆柱坐标转换到同一笛卡儿坐标系,为有限元离散奠定基础.经过有限元推导,求得局部多孔质气体静压轴向轴承的承载能力与静态刚度,并对局部多孔质节流进行试验以验证理论模型的正确性.另外,对局部多孔质节流气体静压轴向轴承和小孔节流气体静压轴向轴承进行对比试验.结果表明:局部多孔质节流和小孔节流静压轴承的承载能力随着气膜厚度的减小而增加;静态刚度随着气膜厚度的增加先增加后减小;局部多孔质节流比小孔节流具有较高的承载能力和静态刚度.     

控制陀螺仪与g 2 / 有关干扰力矩的主要技术途径

一高精度液浮陀螺仪中一般都使用动压气体轴承，动压气体轴承的不等刚度及转子姿态角是陀螺仪ｇ２有关干扰力矩的主要来源，加之由于径向轴承的位移和转子姿态角的出现使问题更加复杂。本文假定框架等刚性的前提下，着重讨论动压气体轴承的某些参数对单自由度液浮陀螺仪与ｇ２有关干扰力矩的影响及其控制此项干扰力矩的技术途径。     

一种滑动轴承试验台的研制与牙轮钻头镶嵌滑动轴承磨擦损性能的台…

在石油钻井中，滑动轴承牙轮钻头的应用日益增多，但轴承的工作环境却相当恶劣。为了提高钻头滑动轴承的工作寿命，并为这类轴承的设计提供科学依据，针对其实际应用工况，特殊设计制造了一种ＩＰＧ－２型滑动轴承试验台，并且利用其在３０ＫＮ、４０ＫＮ和５０ＫＮ的３种载荷条件下，对牙轮钻头镶嵌铜合金的滑动轴承进行了台架试验研究，着重考察了铜合金镶嵌区尺寸之大小对轴承磨擦磨损性能的影响，结果表明，在相邻两个镶嵌区之间     

陀螺电机动压气体轴承间隙误差分析与改进

H型动压气体轴承陀螺电机(以下简称"动压电机")装配后的组合间隙是轴承筛选的关键指标。实际工程中部分动压电机产品的组合间隙与按照轴承零件尺寸计算的间隙相差较大,测量重复性差,合格率较低。为了进一步提高动压电机的一致性和合格率,首先从轴承间隙的测量方法入手,对轴承间隙测量误差建立模型树进行分析,找出了轴承零件尺寸稳定性、多余物以及间隙测量工装是影响轴承间隙测量误差的主要因素,提出了增加稳定处理,优化间隙测量工装,抑制电机污染源,组合清洗等技术改进措施,并通过合理调整间隙控制指标,显著提高了动压电机一致性和合格率。这些思路方法都为动压电机生产量化控制和可靠性筛选提供了很好的借鉴参考价值。     

混合式陶瓷轴承的研制及其台架试验研究：I.制备陶瓷球最佳工艺？…

为了加速航空发动机技术的发展，研制混合式陶瓷轴承是一个值得重视的研究方向，研究这种轴承的关键在于陶瓷球的高效高精度加工，在这方面，常规的磨削加工方法很难满足实用要求，因此，利用一种新的磁流体研磨法加工Ｓｉ３Ｎ４陶瓷球，首先对这种方法的基本原理与装置和研磨实验条件与方法作了简要阐述，进而通过一系列的试验研究，考察了将Ｓｉ３Ｎ４陶瓷球毛坯研磨成成品球的研磨效率分别随驱动轴转动速度，加工载荷和磨粒粒径等     

用于微重力试验的气磁混合悬吊单元研制

传统被动式跟随悬吊法应用中摩擦干扰力大的问题影响了微低重力试验的精度,本文中结合悬吊法和气浮法的优点,利用气体轴承极低摩擦力的特点,设计了一款气磁混合悬吊单元原理样机,以提高被动式跟随悬吊法微低重力试验的精度.首先介绍了气磁混合悬吊单元的工作原理,对气磁模块的布局方案进行了初选,选择了环形气体止推轴承与中央磁吸力单元组合的结构形式.设计了独特的永磁-电磁模块,并对其电磁吸力特性进行了分析,分析结果显示在气隙厚度为0.65 mm左右时,磁力能够保持在2 kN左右,得到了0.3～1.0 mm气隙长度下混合磁单元的磁力及刚度变化曲线.气体止推轴承采用大块多孔石墨作为节流器,能够在较小的空间尺寸中实现最大的承载能力,应用有限元方法对多孔质气体轴承的承载能力进行了分析,并进行了网格无关性分析,确定了计算模型的规模.对供气压力和渗透率等主要参数的影响规律进行了分析,分析结果显示选定的工作参数可在20μm气膜厚度下实现2 kN的承载.完成了气磁混合悬吊单元的结构设计,并试制了3台样机.针对气浮轴承进行了多孔材料渗透率测试.针对气磁混合悬吊单元,考虑到测试的安全性,设计了倒扣拉力法试验装置进行了气磁混...     

箔片-电磁混合轴承的稳态承载特性及控制

箔片-电磁混合轴承(HFMB)是一种将气体箔片轴承和电磁轴承混合使用的新型轴承,有效解决了气体箔片轴承低速磨损大和电磁轴承承载力有限的不足,并且具备载荷可分配和支撑系统动力学性能可调节等优点.文中在分析两种轴承稳态承载特性的基础上详细讨论了混合轴承的稳态控制方法,给出了一种以电磁轴承实际承载力与预分配承载力差值最小为控制目标,通过等边三角形为基本单元对混合轴承工作区域进行划分的箔片-电磁混合轴承稳态工作位置搜索算法.最后建立了系统模型并进行了数值仿真,验证了稳态控制系统的可行性和有效性.     

High-speed electrospindle running on air bearings: design and experimental verification

In high-speed machining there are a number of applications in which the spindle is supported by air bearings. This type of bearings has very low friction and wear, resulting in virtually unlimited life. If the system is designed correctly the radial stiffness on the tool is comparable to that of ceramic ball bearings. A mathematical model of rotor-air bearing system and experimental work on high-speed spindle for machining applications are presented. The model is numerically solved paying special attention to boundary condition of supply ports. The discharge coefficient c _d is considered on the basis of experimental findings. The influence of clearance and supply port diameter is discussed for radial bearings and axial thrust bearings. The aim is to find an optimum solution representing the compromise between high stiffness, supply flow and stability. The prototype of a high-speed electrospindle running on air bearings is described. The rotor, 50 mm in dia. and weighing 7 kg, is designed for 100 krpm. The spindle is driven by a high frequency asynchronous motor featuring closed loop speed control. Experimental stiffness curves are shown at different supply pressure ratings.     

Rotordynamic analysis of systems with a non-linear model of tilting pad bearings including turbulence effects

An analytical model of a tilting pad bearing was developed based on the short bearing assumption with the turbulence effect included. In order to determine its influence on the dynamic behavior of the rotor, this model was compared against one without the turbulence effect through a simulation of a Jeffcott/Laval rotor supported by a couple of bearings. Both models were also used to determine the influence of geometric parameters on tilting pad bearing making use of the aforementioned system at different rotor speeds. When analyzing the results, the parameters which presented the largest influence were: pad preload, number of segments, radial clearance, pad position, and pad pivoting angle. As the pad moment of inertia and the pivoting distance have changed the shaft motion only a few microns, their effects can be neglected. The bearing model with turbulent flow effect has generated higher hydrodynamic forces when compared to the one without this effect, which remarks the importance of considering such phenomenon during the analysis of the high speed hydrodynamic bearings.     

Dynamics of Slider-Crank Mechanisms with Flexible Supports and Non-Ideal Forcing

Transient and steady state dynamic response of a class of slider-crank mechanisms is investigated. Specifically, the class of mechanisms examined involves rigid members but compliant supporting bearings. Moreover, the mechanisms are subjected to non-ideal forcing. Namely, both the driving and the resisting loads are expressed as a function of the angular coordinate describing the crank rotation. First, an appropriate set of equations of motion is derived by applying Lagrange's equations. These equations are strongly nonlinear due to the large rigid body rotation of the crank and the connecting rod, as well as due to the nonlinearities associated with the bearing action and the form of the driving and the resisting loads. Consequently, the dynamics of the resulting dynamical system is examined by solving the equations of motion numerically. More specifically, transient response is captured by direct integration, while determination of complete branches of steady state response is achieved by applying appropriate numerical methodologies. Initially, mechanisms whose crankshaft is supported by bearings with rolling elements and linear stiffness characteristics are examined. Then, numerical results are presented for rolling element bearings with nonlinear stiffness characteristics. Finally, the study is focused on mechanisms supported by hydrodynamic bearings. In all cases, the attention is focused on investigating the influence of the system parameters on its dynamics. Moreover, models with constant crank angular velocity are first analysed, since they provide valuable insight into some aspects of the system dynamics. Eventually, the emphasis is shifted to the general case of non-ideal forcing, originating from the dependence of the driving and the resisting moments on the crankshaft motion.     

基于PID方法的可倾瓦推力轴承分析

使用PID方法控制可倾瓦推力轴承流场求解中轴瓦倾角和支点膜厚的迭代,实现了力和力矩平衡同步收敛.以光滑及粗糙表面下可倾瓦推力轴承流场求解为例,对比PID方法和传统方法,PID法编程便捷,计算效率高,同时能够反映可倾瓦推理轴承的刚度特性.考虑表面粗糙度时,PID法能够求解传统方法不收敛的问题.     

小孔节流气体静压润滑的离散化和计算收敛

通过在雷诺方程式中增加一流量项,以避免求解雷诺方程时,为满足流量条件而求解压力梯度所带来的噪声和误差,并将不同坐标系内的雷诺方程式变换成为相同形式,以简化数值计算;对加权余量法和变分求极值法这2种将微分方程离散化的方法进行了分析;探讨了小气膜时出现发散的原因并提出了应对措施。     

Reduction of subsynchronous vibrations in a single-disk rotor using an active magnetic damper

Rotor instabilities in turbomachinery often manifest themselves as a re-excitation of the first rotor critical speed resulting in lateral rotor vibrations at a frequency below the rotor operating frequency. Considerable work exists in the literature involving the analysis of destabilizing mechanisms and passive solutions for reducing subsynchronous vibrations. The authors propose here a novel active control solution utilizing active magnetic bearing (AMB) technology in conjunction with conventional support bearings. The AMB is utilized as an active magnetic damper (AMD) at rotor locations inboard of conventional support bearings. Presented here are initial proof-of-concept experimental results using an AMD for vibration control of subsynchronous rotor vibrations in a high-speed single-disk laboratory rotor. The study shows that subsynchronous vibrations are reducible with an AMD and up to a 93% reduction in the amplitude of subsynchronous vibrations is demonstrated. The study also shows that the AMD can significantly increase synchronous vibration response (up to 218% in one case) by increasing system stiffness and pushing a critical speed closer to an operating speed. The overall results from this work demonstrate that reduction in subsynchronous response is feasible and that full rotor dynamic analysis and design is critical for the successful application of this approach.     

推力轴承瞬态启动油膜热不稳定性的线性分析

以简化推力轴承为对象 ,理论上证明了推力轴承运行时存在热不稳定性 ,采用小扰动分析法得到了油膜温度的扰动方程 ,应用简正模态分析法推导了无量纲热不稳定性准则数以及推力轴承运行的热不稳定性准则 .     

弹性箔片动压径向气体轴承动特性的实验研究

建立了新型弹性箔片动压气体轴承性能测试实验台,在静载60N、转速9000r／min条件下进行轴承性能测试试验,通过中心插值法获得轴承中心的扰动速度和加速度,采用时域最小二乘法计算不同激振频率下的8个轴承动态线性刚度和阻尼系数,考察了激振频率对轴承动特性系数的影响．结果表明：轴颈中心扰动轨迹为椭圆形且振幅随动态激振频率增加而增大;刚度和阻尼系数的直接项随动态激振频率增加而减小;交叉刚度和阻尼相对激振频率的变化较小,且其值小于直接项;当激振频率与轴颈转动频率相同时,工频成分的影响较大,轴心扰动幅值明显增大,刚度和阻尼的直接项小于其它频率时的值．     

推力轴承热稳定性非线性分析及周期稳态解的全局特性研究

建立了考虑瞬态油膜压力影响的热稳定性分析模型 ,用求解系统周期解分岔的 PNF法对推力轴承系统的热稳定性进行了研究 ,结合 Poincare映射与胞映射法思想 ,提出了用于分析系统周期稳态解全局特性的数值计算 PCM方法 ,并对推力轴承热系统周期稳态解的全局特性进行了考察     

Non-Newtonian effects of second-order fluids on double-layered porous Rayleigh-step bearings

Theoretical study of double-layered porous Rayleigh-step bearings with second-order fluid as lubricant is presented. An approximate method for the solutions of the governing fluid film equations for a porous region is proposed. The expressions for the pressure distribution, load capacity and frictional coefficient are obtained in compact form. Calculations of the dimensionless load capacity, frictional force and frictional coefficients are presented for specific values of the material parameters. It is found that the double porous layer yields an increase in the load capacity and ensures decrease in frictional force at the porous lining as compared with the conventional porous Rayleigh-step bearings. The maximum dimensionless load-carrying capacity is found to occur at a slightly larger step ratio as compared with the conventional porous Rayleigh-step bearings.