燕尾静压导轨初始油膜厚度对静动态性能的影响

燕尾静压导轨的工作性能与其选取的初始油膜厚度密切相关。通过对由PM流量控制器调控的燕尾静压导轨进行研究,分析并推导出初始油膜厚度与静压导轨静动性能之间的函数关系。结果表明：增大导轨底层大面和燕尾面初始油膜厚度,都可以提高导轨的承载能力,但提升幅度不大;降低导轨底层大面和燕尾面初始油膜厚度,均会增大低燕尾导轨的静、动态刚度,其中导轨底层大面初始油膜厚度的变化对静刚度影响更大,燕尾面初始油膜厚度的变化则对动刚度影响更大,在实际中应该根据所设计导轨工况选取合适的初始油膜厚度。     

油膜厚度对闭式液体静压导轨性能的影响

为了研究油膜厚度对静压支承的影响,以闭式液体静压导轨为研究对象,确定了导轨系统的初始参数;基于力平衡方程及流量方程,建立了功率损失、静态性能、动态性能的数学模型;将总功率损失、承载能力和静刚度、固有频率、调整时间和动刚度等参数作为导轨的性能指标,利用MATLAB软件定量分析了油膜厚度对导轨性能的影响。研究结果表明：增大油膜厚度,则液体静压导轨的总功率损失增大,调整时间变长,承载能力不变,静刚度、固有频率及动刚度减小。因此,减小油膜厚度,可降低导轨总功率损失,提高静态性能和动态性能。研究结果为工程实际中闭式液体静压导轨静压油膜的设计提供了理论依据。     

油膜厚度对闭式液体静压导轨性能的影响

为了研究油膜厚度对静压支承的影响,以闭式液体静压导轨为研究对象,确定了导轨系统的初始参数;基于力平衡方程及流量方程,建立了功率损失、静态性能、动态性能的数学模型;将总功率损失、承载能力和静刚度、固有频率、调整时间和动刚度等参数作为导轨的性能指标,利用MATLAB软件定量分析了油膜厚度对导轨性能的影响。研究结果表明:增大油膜厚度,则液体静压导轨的总功率损失增大,调整时间变长,承载能力不变,静刚度、固有频率及动刚度减小。因此,减小油膜厚度,可降低导轨总功率损失,提高静态性能和动态性能。研究结果为工程实际中闭式液体静压导轨静压油膜的设计提供了理论依据。     

矩形空气静压导轨气浮垫的实验性能对比

提出并设计了一种具有弹性薄板可变截面积均压槽的高刚度空气静压导轨气浮垫,用以提高气浮垫的刚度。通过气浮垫性能测试试验台。对新结构气浮垫的承载能力和气膜间隙进行了测定,得到气浮垫的承载力和刚度。通过实验分析,结果表明,在气体压力的作用下,环形弹性薄板产生弹性变形,引起节流面积和均压槽深度的变化,使得新结构气浮垫的刚度较之传统已有气浮垫得到明显提高。新结构矩形空气静压导轨气浮垫具有较广的应用推广空间。     

液体静压导轨及其设计研究

介绍了液体静压导轨工作原理、特点、分类及适用场合，分析了承载能力、油膜刚度、油膜厚度以及导轨间隙等静压导轨设计的影响因素。     

微尺度下空气静压支撑在滑移区的承载特性实验研究

为了阐释空气静压导轨气膜间隙处在微小尺度所体现的特性,引入努森数(Kn),计算了不同工况下气膜内压力和不同气膜厚度下Kn数的变化关系。引入支撑区气膜分层假设,与分子动力学相结合,对气膜内不同流态层的刚度进行了实验和分析。通过ANSYS仿真和实验数据相结合得出了结论:气膜内稀薄效应的增强,可以一定程度上提高气浮支撑的静承载能力。气浮支撑的刚度特性和气膜内部分层情况有关:以分子碰撞运动为主的稀薄层主要起容性效应,实现分子间动量的传递和转化,因此该层所体现出来的刚度较差;以惯性力驱动的连续流层内部分子运动比较稳定,特别是在垂直方向不存在显著的动能和压力能之间的转化,因此该层的刚度特性较强。实验证明,气膜厚度在1~10 μm时,气膜的刚度先增大后减小,也间接论证了静压支撑的刚度特性主要由气膜内连续流层决定。     

波箔型径向气体轴承静态特性分析

建立考虑气体可压缩性和箔片变形的波箔型轴承气膜厚度模型,采用有限差分和松驰迭代法耦合求解Reyn olds方程和气膜厚度方程,得到波箔型轴承气膜厚度和气膜压力分布,并分析波箔型动压径向气体轴承结构参数和运行参数对其静态性能的影响.结果表明:波箔型轴承数值分析结果与相关文献试验数据相符度较好,证明该模型的科学性与精确性;对比箔片轴承和传统刚性表面轴承气膜压力和气膜厚度的分布特点,表明箔片轴承具有更高的承载能力;随着偏心率、转速的增大,箔片轴承承载能力增大,偏位角减小;随着转速增大,气膜压力提高,箔片变形增大,最小气膜厚度增大.     

新型气体静压支承技术的研究

介绍了气体静压支承的工作原理,针对精密加工设备开式气体静压支承工作过程中存在的漂移和运动不稳定问题,提出采用负压发生器与节流器相结合的新型负压吸附静压支承技术,应用仿真软件对负压吸附静压支承中的小孔节流和多孔质节流形式进行了分析探讨,分析了负压吸附静压支承的工作原理、间隙压力计算方程和气膜刚度的计算;通过试验测试分析该技术,保证了开式气体静压导轨所需的气膜厚度和刚度;将该技术应用到精密数控机床导轨中,使机床抗振性和运动精度得到提高。     

三轴向振动台运动耦合装置的参数优化

通过建立三轴向振动台运动耦合装置的传递模型,根据需求频率范围合理选择运动耦合装置刚度。采用有限元方法求解气体润滑问题,仿真分析了供气压力和气膜厚度对气体静压轴承刚度的影响。结果表明,气体静压轴承的刚度随着供气压力的增大而增大,在特定的供气压力下存在一个使气体静压轴承的刚度取得极值的气膜厚度极值点。在此基础上,优化得到一组满足运动耦合装置传递特性要求的供气压力和气膜厚度参数,并通过原理样机进行了验证。实验结果表明,优化得出的运动耦合装置参数满足传递特性要求。     

定量供油开式液体静压环形导轨油膜厚度研究

简要介绍了定量供油开式液体静压环形导轨的结构、工作原理,并进行了油膜厚度计算及油膜刚度分析,可为该种静压导轨油膜厚度的确定提供参考。     

基于流固耦合的波箔动压气体轴承承载性能优化

基于有限元软件Ansys Workbench,建立波箔动压气体轴承在可压缩流体介质中运动的有限元模型,采用6DOF动网格计算方法对轴承的运动状态进行流固耦合数值模拟,探讨不同转速和波箔片结构参数（波箔的长度比、高度以及厚度）对轴承承载性能的影响规律。结果表明：轴承气膜压力大小的分布与平箔片变形量的大小成对应关系,说明提出的流固耦合方法能很好地反映波箔动压气体轴承的润滑状态;随着转速的增大,轴承动压效应不断增强,承载力增大,且平箔片的结构变形不断增大,致使气膜压力的收敛区发生波动;随着波箔的长度比和波箔片厚度的增加,轴承承载力先快速增大后趋于稳定,而波箔片高度对承载力影响不大,表明适当增加波箔的长度比和波箔片厚度可以提高承载力。     

Numerical analysis on nanoparticles-laden gas film thrust bearing

Nanoparticles can be taken as additives and added into various fluids to improve their lubricating performances. At present, researches in this area are mainly concentrated on the improvement effects of nanoparticles on the lubricating performances of liquid such as oil and water. Nanoparticles will also affect gas lubrication, but few related studies have been reported. Nanoparticles-laden gas film (NLGF) is formed when adding nanoparticles into gas bearing. Then, the lubricating performances of gas bearing including pressure distribution and load-carrying capacity will change. The variations of pressure distribution and load-carrying capacity in nanoparticles-laden gas film thrust bearing are investigated by numerical method. Taking account of the compressibility of gas and the interactions between gas and nanoparticles, a computational fluid dynamics model based on Navier-Stokes equations is applied to simulate the NLGF flow. The effects of inlet nanoparticles volume fraction and orifice radius on film pressure distribution and load-carrying capacity of the NLGF are calculated. The numerical calculation results show that both of the film land pressure and the maximum film pressure both increase when the nanoparticles are added into gas bearing, and the film pressures increase with the rising of the inlet nanoparticles volume fraction. The nanoparticles have an enhancement effect on load-carrying capacity of the studied bearing, and the enhancement effect becomes greater as the film thickness decrease. Therefore, nanoparticles can effectively improve the lubricating performance of gas bearing. The proposed research provides a theoretical basis for the design of new-type nanoparticles-laden gas film bearings.     

Pressure and Flow Studies of an Experimental Externally Pressurized Gas Lubricated Bearing

An externally pressurized, gas lubricated bearing for obtaining both axial and radial support is described. The manner in which this “integral journal-thrust bearing” operates is explained, thus demonstrating its superior load-carrying capacity, stability, and stiffness characteristics. Detailed comparative pressure and flow data is presented for both the “integral journal-thrust bearing” and a conventional bearing.     

螺旋槽狭缝节流动静压气体止推轴承静态特性

为优化动静压气体止推轴承的承载特性,设计一种具有螺旋槽和狭缝节流器结构的动静压气体止推轴承,采用Fluent对轴承静态特性进行仿真分析,通过改变主轴转速、供气压力,研究气膜厚度、螺旋槽宽度、狭缝厚度等参数对轴承静态特性的影响。结果表明:相对狭缝节流止推轴承,增加螺旋槽结构可以提升轴承的动压效应增强,从而提升轴承的承载力和刚度;相同条件下,气膜厚度越大,轴承的承载力和刚度越小;主轴转速和供气压力增加,承载力和刚度均提升明显;螺旋槽宽度增加,轴承的承载力和刚度先增大后减小;狭缝厚度增大,轴承的承载力先增大后不变,刚度先增加后减小;狭缝深度提升,轴承的承载力减小,刚度先增大后减小。     

Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 1: Experiment and theory

In this paper, the load-carrying capacity, power losses and stiffness of disk-type hydrostatic thrust bearings including the case of eccentric loading are discussed theoretically. The numerical analysis method is established based on a two-dimensional elastohydrostatic problem with an elastic deformation model, which is extended to adapt it for a non-axisymmetric load acting on the thrust bearing. The bearing is made of a combination of stainless steel/stainless steel and stainless steel/plastics. For the elastic materials, the maximum stiffness derived from, i.e., minimum film thickness is, larger than that of the rigid material in the range of a large ratio of pocket pressure and a hydrostatic balance ratio of over unity, which is defined as the ratio of the load to the maximum hydrostatic load-carrying capacity. The maximum load-carrying capacity and minimum power loss can exist in the domain of the hydrostatic balance ratio over unity for the case of the bearing consisting of elastic/rigid materials, in comparison with that composed of the same rigid materials. For the case of water, the power loss due to leakage flow is slightly larger but that due to frictional torque is much smaller than that in the case of hydraulic oil. Then, the total power loss is much smaller than that of hydraulic oil.     

The influence of the molecular mean free path on spherical thrust gas bearing performance

The performance of a spherical thrust gas bearing under slip flow conditions was investigated and it was shown that as the ratio of the mean free path to the minimum film thickness increased the bearing load-carrying capacity and the lubricant mass flow rate increased while the frictional torque decreased. The effect is more pronounced at lower values of inlet pressure and film thickness.     

A Comparative Study of Static and Dynamic Characteristics of Parabolic and Plane Inclined Slider Bearings Lubricated with MHD Couple Stress Fluids

In this article the couple stress effects on the static and dynamic characteristics of parabolic and plane inclined slider bearings in the presence of an applied magnetic field with squeeze action is analyzed theoretically. The modified magnetohydrodynamic (MHD) couple stress Reynolds equation is derived. The closed-form solution for the film pressure of parabolic and inclined plane slider bearings is obtained and used to study the MHD couple stress static and dynamic characteristics of these bearings. The results predict a higher steady load-carrying capacity, dynamic stiffness, and damping coefficient for the bearings lubricated with MHD couple stress fluid than the corresponding Newtonian case. It is observed that the parabolic-shaped slider bearings provide greater steady load-carrying capacity, dynamic stiffness, and damping coefficients compared to the plane inclined slider bearings.     

Incompressible and Analytical Study on an Out-Pump Type Complex Thrust Gas Bearing

ABSTRACT

The structure of an out-pump type thrust gas bearing was described, and an analytical model was developed under completely incompressible condition. The objectives were to investigate the coupling between aerodynamics and aerostatics in a complex thrust gas bearing and to improve the performance of the bearing. The model showed that the load-carrying capacity had five parts to it and that apparently there were pressure coupling and structure coupling between aerodynamics and aerostatics. The surface feature function was identically positive: it increased the load-carrying capacity greatly. There was also no limit regarding the pressure ratio—when the pressure ratio was 0, the load-carrying capacity increased to about 25%.

     

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...