静压径向气体轴承静态特性数值分析

对静压径向气体轴承的静态特性进行了详细的理论研究,采用二阶有限差分方法数值求解无量纲雷诺方程,编制Matlab迭代程序计算轴承的气膜压力分布。仿真分析了各种轴承结构参数和工作参数下静压气体轴承的承载、刚度和质量流量等静态性能的变化规律。仿真结果表明轴颈的转速对静压气体轴承的承载、刚度和质量流量等静态特性施加着重要影响,在分析轴承性能时必须考虑轴颈的旋转效应。当轴颈的转速不断增大时,轴承的气膜压力、承载能力和稳态刚度等静态性能能够得到显著提升。     

小孔节流静压止推气体轴承静特性的数值分析

介绍了计算流体力学软件 FLUENT 及其在气体轴承研究中的应用.针对环形小孔节流静压止推气体轴承,基于 FLUENT 软件进行了简化假设并建立了计算模型,利用 FLUENT 软件对止推气体轴承模型进行了数值分析,求解了环形小孔节流静压止推气体轴承的压力场分布、耗气量和承载能力等轴承静特性,并成功捕捉到了大气膜间隙下供气孔周围的压力突降区.对计算结果进行了分析,并与文献计算值以及试验值进行了对比,验证了数值分析的可靠性.     

非均匀供气静压气体径向轴承的静特性分析

非均匀供气可以实现静压气体轴承的刚度调节,增强轴承的承载能力。为了探究非均匀供气条件对静压气体轴承内压力分布和静态特性的影响,以双排供气径向气体轴承为研究对象,采用数值计算对不同供气方式(变压供气孔位置、区域范围)和供气压力下轴承的静态特性进行了研究。数值计算结果表明:变压供气孔的位置对轴承的静特性有较大影响;当在主要承载区内增大供气压力时,可显著增强轴承的动静压效应;增加压力可变的区域范围有助于提升轴承承载力,但耗气量也相应有所增加;增加承载侧供气压力和减小非承载侧供气压力都可以有效提升轴承承载力,后者还可以减小气体总流量;承载侧与非承载侧的供气压差越大,越有利于轴承承载力的提升。     

静压气体轴承静刚度的动态测试新方法

以环面节流静压气体球轴承为例,建立轴承动静态刚度与气膜位移-动态力频响函数的数学模型;借助数学分析和数值试验,从理论上揭示了轴承气膜位移-动态力频响函数与气膜静刚度、动刚度之间的联系,指出静压气体轴承静刚度的测量可以通过测量低频下气膜频响函数的幅频特性来代替.介绍球轴承气膜幅频特性测试装置的工作原理及测试系统固有模态对测试结果的影响.实测结果表明,静压气体轴承静刚度的动态测试新方法是正确可行的,气膜与承载质量构成的本质非线性二阶振动系统,其低频段的动态刚度数值仍然等于该工作点处的静刚度.新的测试方法,能够实现轴承静态刚度的在线自动测试,提高静刚度的测试精度和效率;将激振频率扩展到机械系统通常涉及的频段后,可以同时得到轴承的动静态刚度和气膜位移-动态力的幅频特性,这对于气体轴承稳定性及精密轴系动态性能的研究具有重要的意义,是轴承的静态测试所无法实现的.     

基于FLUENT的径向静压气体轴承的静态特性研究

以径向静压气体轴承为研究对象,研究动压效应及偏心率对轴承静态特性的影响,采用三维建模,结构化和非结构化网格相结合,运用有限体积法对三维稳态可压缩N-S方程进行求解.结果表明:承载能力随着偏心率的增大而增大;大偏心率高转速时,动压效应对承载能力的影响不可以忽略;大偏心率时,随着转速增加,沿旋转方向,最小气膜间隙处的压力分布不断增大;当转子静止时,刚度随偏心率的增大而先增大后减小;高转速时,刚度随偏心率增加而增加;计算结果与试验结果的对比表明该计算方法能够有效进行径向静压气体轴承流场特性分析.     

气体静压多孔质球面轴承静态性能分析

与传统的小孔节流气体静压轴承相比,气体静压多孔质轴承具有高承载能力、高阻尼和很好的稳定性等。气体静压多孔质球面轴承具有合力始终对准球心,轴承运转平稳等优点,既具有轴向限制同时具有径向限制,在工业当中应用相当普遍。给出了球面轴承的理论分析、有限元推导过程,基于有限元推导过程给出了球面轴承的理论计算静态性能。在自行研制的试验台上进行气体静压试验,由此得到轴承的静态性能。试验结果和理论计算结果之间的吻合良好,从而说明理论计算的正确性和可行性。     

小孔节流静压气体轴承压降效应的数值分析

孔式节流静压气体轴承存在的压降效应会降低轴承承载性能。为探讨不同轴承结构参数对节流孔出口处压降效应的影响,以小孔节流静压气体轴承为研究对象,采用有限差分法、超松弛迭代法对轴承气膜流场进行计算,得到不同轴承结构参数下气膜压力分布。结果表明：节流孔直径和数量、偏心率、节流孔位置以及平均气膜厚度均对节流孔的压降效应产生重要影响;压降效应随节流孔直径和数量的增大而减小,随平均气膜厚度和偏心率的增大而增大,随空气温度升高而降低;节流孔越靠近轴承端面,压降效应越强;转速变化对节流孔压降基本不产生影响,表明压降效应主要与轴承的静态特性有关,与动态性能关系很小。     

小孔节流深浅腔动静压气体轴承承载特性分析

以小孔节流深浅腔动静压气体轴承为研究对象,采用Fluent软件对轴承的承载特性进行分析,研究偏心率、供气压力、主轴转速、气膜厚度、浅腔深度比等因素对轴承承载力和刚度的影响。结果表明:小孔节流深浅腔动静压气体轴承浅腔区的平均压力大于深腔区的平均压力,压力最大区域出现在浅腔末端靠近轴承端面处;随着供气压力的增加,承载力逐渐增大,但供气压力不应超过0.95 MPa;当主轴转速在3×10⁵ r/min以内时,承载力和刚度随着转速的增加呈线性增长规律,当主轴转速超过3×10⁵ r/min继续增加时,承载力和刚度的增长趋势明显放缓;承载力与刚度随着浅腔深度比的增加先增大后减小,当浅腔深度是气膜厚度的1～1.5倍时,承载力与刚度接近最大值。     

双排孔静压止推气体轴承的静动态特性研究

针对双排孔供气的静压止推气体轴承,设计周向环形均压槽以提高轴承的承载力和静刚度,建立气膜模型并对其进行Fluent仿真,研究其结构参数对静态特性的影响规律.仿真结果表明:当气膜厚度h=10μm时,供气孔数n=16,孔排间距△d=25 mm,外、内径比值C=4.0,均压槽槽宽d1=6 mm,槽深h1=0.02 mm,节流...     

边界元方法在研究气体静压轴承静特性中的应用

本文应用边界元方法研究了在二维流动假设下，气体静压圆柱轴承的静态特性。并将其计算结果与其它分析方法的计算结果进行了比较，证明了该方法在这一领域应用的可行性。     

环形节流孔径向静压气体轴承的数值仿真

以环形节流孔径向静压气体轴承为研究对象,介绍了静压气体轴承的结构形式和工作原理,对气体润滑理论基础Reynolds方程进行了分析,利用计算流体动力学软件FLUENT对气体轴承的流场进行仿真分析,求解出了轴承气膜的压力分布.在轴承几何参数不变的情况下,分析了承载力与空气质量流量随不同供气压力和偏心率变化关系,并研究了静压气体轴承在高速工作下,动压效应对承载力的影响.     

Design of aerostatic flat pad bearings using pocketed orifice restrictors

Design charts are presented to enable the design of aerostatic thrust bearings which use pocketed orifice restrictors. Attention has been paid to ensuring that pneumatic hammer instability is avoided by providing design information on the maximum depth and diameter of the orifice pocket. The design procedures presented are based upon analyses produced using finite difference equations to the compressible form of the Reynolds equation. The procedures presented provide the designer with a graphical technique that enables him to take into account stiffness, clearance, number of orifices and bearing dimensions when deriving a satisfactory solution to his problems.     

Design of aerostatic flat pad bearings using annular orifice restrictors

Design charts are presented for use in the design of aerostatic thrust bearings which use annular orifice restrictors. Annular orifices are preferred when pneumatic hammer instability is a potential problem. The design procedures presented are based upon analyses produced using finite difference equations to the compressible form of the Reynolds equation. The method provides the designer with a graphical technique that enables him to take into account bearing stiffness, clearance, number of orifices and bearing dimensions in obtaining a satisfactory solution to his problem.     

油腔式静压轴承的动特性和稳定性近似分析

本文在小扰动条件下，利用流量连续方程推导出油腔式静压轴承的刚度和阻尼系数的近似计算公式。     

The design of high efficiency flat pad aerostatic bearings using laminar restrictions

The design of flat pad aerostatic bearings is examined to determine the best inlet arrangement to achieve high load capacity. The paper shows that like all other forms of aerostatic bearings, the optimum selection of supply to inlet pressure (K_g) and the optimum position of inlet devices can be achieved. The paper demonstrates a relatively new type of inlet geometry — the capillary inlet slot. Both single thrust pad and opposed flat pad bearings arrangements are examined. A theoretical analysis of the flat pad arrangements has been developed using a finite difference approach previously adopted for the analysis of externally pressurized journal bearing arrangements¹.     

Theoretical analysis of two configurations of aerostatic flat pad bearings using pocketed orifice restrictors

Aerostatic flat pad bearings are finding increased applications in high-precision machine tools, high-performance measuring equipment and coordinate measuring machines. To date, much of the development of these bearings has been of an empirical nature since there are no detailed design procedures for assisting designers to optimize their designs^1,2. In the field of aerostatic journal bearing design, comprehensive procedures do exist. The object of this paper is to exploit the principles developed for the analysis of aerostatic journal bearings to the area of flat pad bearings, which are more widely used in industrial situations. In this paper, similar analysis tools are developed and are used to obtain design performance data for a number of flat pad bearing configurations. These data include load, flow and stiffness parameters, all of which are fundamental to design optimization.     

Improvement of static characteristics of an aerostatic journal bearing using the elastic deformation of an O-ring

A new type of aerostatic journal bearing in which the elastic deformation of an O-ring is used to improve its static characteristics is proposed. The static characteristics of this bearing are determined theoretically by both the finite difference method and the small perturbation method. Effects of parameters on the static characteristics are shown, and the optimum design method for the static characteristics is discussed. Further, theoretical results are compared with experimental results to confirm the validity of theoretical predictions. It is consequently found that the new type of bearing possesses higher static stiffness and greater load capacity than conventional point source bearings with inherently compensated feeding holes.     

Static tilt characteristics of aerostatic rectangular double-pad thrust bearings with compound restrictors

Aerostatic rectangular thrust bearings with compound restrictors have often been used in ultra-precision machine tools and precision measuring equipment because high bearing stiffness is easily achieved. Compound restrictors combine a feed-hole restrictor with a groove compensation restrictor. This paper investigates, theoretically and experimentally, the static tilt characteristics of aerostatic rectangular double-pad thrust bearings with compound restrictors, when coupled loads or offset loads are applied. Furthermore, the usefulness of aerostatic thrust bearings with compound restrictors is clarified by comparison with the characteristics of conventional aerostatic thrust bearing with feedhole restrictors.     

Experimental investigation into the performance of an aerostatic industrial thrust bearing

Load and flow versus air-gap curves and stability maps have been obtained for an industrial externally-pressurized air-lubricated thrust bearing with a central restrictor. Supply pressure and pocket depth were treated as parameters. Bearing stiffness was estimated by using a computer to fit a polynomial type curve to the test data. The results show that whereas the effect of inserting a pocket into the bearing improves its load capacity, there is no significant improvement in film stiffness at design conditions. The suggestion is made that the diameter of the orifice in the restrictor should be increased. As pocket depth is increased beyond the design value the bearing becomes prone to pneumatic hammer.     

Zero-compliance aerostatic bearing for an ultra-precision machine

A new type of active air film restrictor is proposed for obtaining a zero-compliance aerostatic thrust bearing. The moving member in the active retrictor is sopported elastically. This active restrictor can therefore be called an aerostatically controlled-restrictor (ACR). Experiments show that the compliance of the thrust bearing with the ACR can be less than 1 nm N⁻¹ when the frequency of the applied load is less than 2 Hz. Pneumatic hammer does nor occur during the experiments.