Analysis of Externally Pressurized Circular Thrust Gas-Bearing with Multiple Supply Holes

An externally pressurized circular thrust gas-bearing with multiple supply holes and no recesses is investigated theoretically by means of the complex potential theory.

By using a suitable potential function which satisfies the boundary conditions, the authors obtain theoretically the pressure distribution and volume rate of flow for both an incompressible fluid and a compressible fluid, and load capacity for an incompressible fluid. Then they find the optimum radial position of supply holes which gives the largest load capacity.

The theory can be extended to any number of the supply holes.     

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.     

Tri-Conical Gap-Shaped Externally Pressurized Gas Bearing Pads

Externally pressurized gas (EPC) bearing pads with convergent conical shapes can provide high load capacity and high stiffness. Research has revealed that if the suitable combination of gap difference and working gap height is chosen, the optimized diameter ratios for stiffness and load capacity are close to the same value, about 0.8 to 0.9, or the ratio of the diameter of the conical gap-shaped part over the pad diameter. The optimized diameter ratio is independent of the supply pressure, the pad diameter and the number of conical parts. Conversely, the stability of the bearings is controlled by the combination of the diameter ratio and the gap difference. From the analysis of the stability criteria and the optimized diameter ratio, the concept of the tri-conical gap-shaped EPG bearing pads was proposed. Numerical and experimental investigation shows that under the same stable conditions, tri-conical gap-shaped pads provide higher stiffness and higher load capacity than simple conical or parallel gap-shaped pads.     

Omni-Directional Support of Spheres Using Externally Pressurized Gas Lubricated Bearing Pads

The advantages of using a multiplicity of externally pressurized gas lubricated thrust bearing pads to completely support a sphere are discussed. The minimum number (six) of pads that can provide all-axis, isoelastic support must be arranged in three opposed pairs to form a mutually orthogonal system. Analytical expressions for the load capacity of such a system are given. It is proven that only this type of support system (six pads or multiples thereof) can provide isoelastic support.

An experimental apparatus, used to determine the operational properties of a six-pad spherical support system, is described. Experimental curves of sphere deflection vs. source pressure for various loads are given and compared with theory.     

径向小孔静压气体轴承的试验研究

本文对多排小孔静压气体径向轴承的静、动特性及稳定性进行了研究，将试验数据与理论结果和中压透平膨胀机气体轴承运行数据进行了对比，并分析了影响轴承性能的各种因素。     

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。     

Analysis and Design of Externally Pressurized Gas Bearings

Equations for flow rate, pressure, load, and stiffness of externally pressurized thrust and journal bearings are given for purely viscous, isothermal gas films with longitudinal or radial flow and no relative surface motion. Charts are presented by means of which the bearing characteristics can be evaluated in terms of the bearing parameter, the bearing configuration, and the ratio of supply to ambient pressure. Sample characteristics of thrust and journal bearings are established using the curves and experimental confirmation shown. A method of treating bearing films with two inlet-restricting orifices in series is described.     

多供气孔静压圆盘止推气体轴承的参数设计

采用工程计算方法研究了按最大静刚度准则设计多供气孔环面节流静压圆盘止推气体轴承几何参数的基本过程,详细讨论了供气孔数和供气孔直径参数对轴承静态性能的影响。随供气孔直径的增大,轴承消耗的体积流量增大,承载力也随之增大,但小气膜高度时增加值较小,大气膜高度时增加值较大,且轴承的最大静刚度逐渐减小。大的供气孔直径,可使轴承在更大的气膜高度下工作。供气孔数对轴承性能的影响与供气孔直径参数相似。理论优化的结果表明,圆盘内径参数应尽量取小值,供气孔分布圆半径应取圆盘内外径的均方根。对不能采用理论优化的几何参数,在数值分析的基础上,给出其合理取值范围。供气孔直径应在0.4~0.8 mm范围内取值,供气孔数应在5~8范围内取值。     

THD Analysis of Non-Constant Gap,Externally Pressurized Conical Bearings

This paper presents a thermohydrodynamic analysis of non-constant gap conical bearings, externally pressurized through the central recess and rotating with a uniform angular velocity. The fluid is assumed to be incompressible and the viscosity of the lubricant is assumed to vary exponentially with temperature. The governing system of coupled momentum and energy equations, in conical coordinates, is solved numerically using the finite difference method to determine various bearing characteristics. Results for convergent, constant and divergent gaps have been presented. It is observed that as the slider is cooled the load capacity and torque of the bearing increase, for both convergent as well as divergent gap. This effect is most accentuated for higher values of film thickness parameter.     

轴向缝切向进气轴颈轴承稳定性的试验研究

本文设计了组合式及嵌入式轴向缝切向进气轴颈轴承,将其装配到与１５０Ｎｍ＾３／ｈ制氧机配套的中压透平膨胀机上进行试验,实测了不同设计参数下的轴承失稳转还,并分析了影响轴承失稳转速的各种因素。     

静压气体轴承稳定性计算方法的分析

对静压气体轴承稳定性的计算方法进行了分析,论述了适合于求解雷诺方程散后的非线性方程组的当前数值计算方法。     

Performance of Externally Pressurized Grooved Thrust Bearings

Externally pressurized grooved gas thrust bearings for shaft systems were studied both numerically and experimentally. Three thrust bearings composed of a symmetric pair of rings facing a shaft collar were tested. The rings, with inner and outer diameters of 52 and 110 mm, respectively, are equipped with a polar array of eight holes, with a 0.35-mm diameter, distributed on a 65-mm-diameter circumference. The influence of a circumferential groove situated in correspondence with the supply holes is discussed. In particular, two thrust bearings have a rectangular cross-sectional groove of 0.7-mm width and 10- and 20-μm depth. A numerical model based on Reynolds' equation is used to study thrust-bearing performance in relation to geometry (diameter of supply holes, clearance, and groove dimensions). A test rig is used to monitor thrust-bearing axial load capacity and stiffness, and evaluate damping and stability at different supply pressure rates. Experimental and numerical results are compared and discussed.     

环形进气锥腔结构静压气体轴承性能研究

中心进气锥腔轴承承载力较高,但气腔容积较大,稳定性较差。对中心进气锥腔轴承结构进行改进,提出环形进气锥腔气体轴承;建立供气孔和轴承间隙组成的完整气体轴承流场,采用层流模式计算不同轴承结构参数时的压力分布、承载力和气容比,并计算优化结构的轴承的承载力和刚度。结果表明,在一定范围内增大锥腔高度和锥腔半径可以提高承载力,增大气容比;改进后的气体轴承承载力和刚度较高,气腔容积大大减小,稳定性提高。     

空气动静压径向轴承实验台加载装置误差分析

通过对空气动静压径向气体轴承实验台加载机构进行力学分析,建立相应的力学模型,并构造出误差函数,进行了误差计算与分析,消除了由于加载机构的弹簧拉力方向角度误差对测量气体轴承气膜支持力的影响.     

气体静压轴颈-止推串接型轴承涡流力矩的有限元分析

采用有限元方法研究了制造误差对狭缝节流气体静压轴颈-止推串接型轴承的涡流力矩的影响，主要分析了狭缝宽度误差和轴颈圆度误差对涡流力矩的影响，以及轴颈的不同安装角度、偏心等因素对涡流力矩的影响。经对比验证表明，有限元计算结果与实测结果基本一致，研究结果对于气体静压轴颈-止推轴承的设计、装配优化和性能预测具有重要的指导意义。     

一种球面气体静压轴承的建模与仿真

介绍了一种小孔节流式球面气体静压轴承,该轴承的加工工艺性较好,而且在各个方向上都有较大的支承力;针对该轴承支承力的计算提出了一种有限划分计算方法,在建模中考虑到气膜压力分布的不对称性,将轴承根据节流孔的数目划分为数个等分,对每个等分再进行有限划分,若划分数足够多,可以认为在每个小等分中的气膜压力沿划分方向无变化,以小等分中心的压力代替,从而简化了轴承的气膜压力分布的求解;借助MATLAB软件队轴承的支承性能进行了仿真计算,并通过实验进行比较验证,实验结果与仿真结果基本一致。     

Theoretical Investigation of Externally Pressurized Thrust Collar Gas-Bearings

Externally pressurized thrust collar gas-bearings with several supply holes are investigated theoretically. The gas supply holes are spaced circumferentially and communicate, directly with the film without feeding into recesses.

A complex potential function which satisfies the boundary conditions of the bearing is found, and the pressure distribution, quantity of flow, and load capacity are calculated for the two cases where there are or are not radial grooves between the holes.

The theory is applicable for any number of gas supply holes.     

带有锥形气腔的平面气浮轴承的流场计算分析

该文采用纯黏性润滑方程和层流N-S方程,对带有锥腔的静压气体润滑轴承内的压力分布作了理论上的研究.通过通流面积和马赫数的计算深入分析了随着气膜厚度的变化,轴承流场内压力的变化及变化机理.通过实验证明,在轴承间隙很小时两种方程求得的压力值与实验结果是一致的.但随着气膜厚度的增加,采用纯黏性润滑方程计算的偏差很大,而采用N-S方程计算的结果与实验结果基本一致.并通过与环面节流的平面轴承的压力对比,表明增大气膜入口处的节流面积, 可以增加轴承的质量流量,提高轴承内的压力,避免较大供气压力和较大膜厚时气膜入口附近压力急剧下降,从而提高轴承承载能力.     

小孔节流静压气体轴颈轴承主轴系统的动态特性分析

通过对小孔节流静压气体轴颈轴承的雷诺方程与描述主轴系统的动力学数学模型联立直接进行数值求解,分析了轴承系统的动力学特性,研究了在不平衡质量作用下轴承主轴系统的响应。结果表明,由于精密离心机小孔节流静压气体轴承的支承刚度大,承载能力高,旋转主轴的运动是稳定的。但在一定条件下,旋转主轴有可能出现不稳定现象,这取决于主轴绕固联坐标系各轴之转动惯量间的关系、轴承支承刚度、主轴旋转速度和不平衡质量控制等因素。该方法用于精密离心机静压气体轴承主轴系统动力学的数值计算,提高了计算精度和可靠性。     

带有圆周方向均压槽的静压气体止推轴承的气锤自激

通过开设均压槽,可以增加静压气体轴承的承载能力和刚度,但是如果气体轴承的均压槽等参数设计不合理,会出现一种振动现象——气锤自激振动,尤其是设计高压重载气体止推轴承时。针对常用的圆盘止推气体轴承,建立轴承活动件的动力学方程,再运用小扰动方法和流量连续性方程得到了气锤自激振动的稳定性判别方程。通过求解稳定性判别方程,发现供气压力越大,自激振动的倾向性越强;气膜间隙在一定范围内容易引起自激振动;节流孔直径越大,自激振动的倾向性越强;当止推轴承的外径和内径的比值比较小时,容易发生气锤自激。通过计算得到了不发生气锤自激振动的轴承设计参数,可用于高压重载气体止推轴承的设计。