数值模拟在静压轴承系统中的应用

为使静压轴承系统在特定负载下能使轴与瓦之间保持液体摩擦状态，采用有限元法，借助ANSYS软件和编制的子程序求解了N—S方程的简化形式——雷诺方程，计算得出一定负载下保持液体摩擦状态所需的油腔供油压力、流场的速度分布、压力分布。根据计算结果设计了某选矿厂静压轴承系统，现场使用表明，该系统工作稳定、节能显著。     

闭式液体静压导轨设计研究

液体静压导轨具有磨损小、运动精度高、平均无故障时间长、驱动功率小、承载力大、刚度高、吸振性好、运动平稳等优点,广泛应用于精密数控机床。但液体静压导轨的相关设计资料较少,该文从导轨形式、油腔结构、油膜厚度、供油方式、节流方式、油液选择、制造材料等方面出发,对液体静压导轨的设计流程进行了总结分析,并设计了一种小型磨床使用的不等面积对置闭式液体静压导轨。     

供油孔区域惯性效应对液体静压推力轴承承载力的影响

分析了液体静压推力轴承供油孔区域惯性效应对其承载力的影响,供油孔区域惯性效应主要影响浅油腔液体静压推力轴承的承载力,当油膜厚度比大于5时,考虑和不考虑供油孔区域惯性效应的承载力之间的相对误差小于1％.对于浅油腔液体静压推力轴承,供油孔区域的惯性效应不容忽视,轴承承载力在考虑和不考虑供油孔区域惯性效应时的相对误差受供油孔...     

速度滑移影响下液体静压止推轴承静态性能分析

为了研究微尺度下速度滑移对液体静压止推轴承性能的影响,将速度滑移模型引入传统雷诺方程中,得到修正的雷诺方程;通过求解修正后的雷诺方程,得到速度滑移影响下八油腔液体静压止推轴承的静态性能特性。研究结果表明:速度滑移的存在并没有改变轴承性能的变化趋势,但使得相同油膜厚度下油膜压力、轴承承载力和刚度增大;随着滑移长度的增大,轴承油腔压力、承载力及刚度增大,最优油膜厚度变小;轴承的承载力和刚度随着供油压力的增大而增大,供油压力相同时,速度滑移使得轴承承载力和刚度有一定程度的增大。     

节流器的改制

节流器是定压供油式液体静压轴承或液体静压支承的主要元件,定压供油式液体静压轴承或静压支承工作性能的好坏很大程度上取决于节流器的型式和参数。 我厂应用的原苏联产52345n滚齿机的节流器是一组合型缝隙节流器。其结构如图所示,它有一个进油口P_1和6个出油孔P_2,6个出油孔分别接入6个油腔来支承卡盘。在节流器壳体内侧有一轴向油槽,在心     

数控外圆磨床砂轮架闭式静压导轨的设计

介绍了数控外圆磨床砂轮架闭式静压导轨的设计过程.重点分析了导轨的分类和液体静压导轨的工作原理及特点.根据当前磨床的设计要求,对液体静压导轨的结构进行了选择,并采用了闭式静压导轨结构.通过对闭式静压导轨上下油腔参数计算,验证了闭式静压导轨的各个设计参数的合理性.结果表明,磨床采用了闭式静压导轨结构后,性能可靠,精度稳定....     

卸荷静压导轨在立式磨床上的应用

重点介绍了采用定压供油的圆台立式磨床卸荷静压导轨的特点及设计计算方法.     

不等腔薄膜反馈式环形静压导轨设计

由两个或4个环形静压导轨组成的高精度、低摩擦、短行程的往复运动机构在机械装备中有很好的应用前景。在导轴的轴向上作往复运动的导套沿周向通常加工有两对油腔,当主承载方向上的成对油腔面积大于辅助承载方向上另一成对油腔时,导套在主承载方向上便具有更大的承载能力。加之,与成对油腔相连接的节流器采用薄膜反馈式节流器,当导套承受外载荷时节流器薄膜发生变形,改变了薄膜两边的节流液阻,促使薄膜两边的出油压力进一步增减。两者叠加,导套在主承载方向上进一步提高了承载能力。对于不等腔薄膜反馈式环形静压导轨参数设计及导套承载力,提出了1种新的计算方法。采用这一方法设计出的大理石静压排锯已应用于生产中,且不同偏心率下的导套承载力的计算结果与试验结果吻合较好,证明该理论模型的正确性。     

重型机床垂向导轨副应用恒流闭式静压导轨的设计

介绍了静压导轨的特点和应用状况,全面阐述了将静压导轨技术应用于重型机床垂向导轨副的设计过程,包括工作原理、油膜刚度、油腔布置、供油回油系统、系统调试测试及该技术的应用成果和范围。     

动静压油膜轴承计算中的几个问题

动静油膜轴承的设计计算比动压或静压轴承要复杂一些。苏联介绍了用电模拟法计算在没有静压供油的情况下封闭的静压油腔压力。美国的S.Heller等和M.F.Hessey求解动静压混合作用时,预先给定油腔压力,然后分别应用小孔或毛细管流量公式估算出下一次求解雷诺方程时的给定油腔压力。如此反复计算直至最后一次求解出的油腔压力值与给定的油腔压力值之差的绝对值小于某定值。则这最近一次求解出的油腔压力值     

球磨机静压轴承静态压力场及流场仿真分析

针对多油腔静压轴承压力油流动的复杂性,使用通用流体有限元软件CFX对油膜进行数值模拟,分析了静态下的油膜压力及流场对静压轴承承载能力的影响.结果显示,圆形主油腔使压力场及流场稳定、均衡;不同的进油速度影响到副油腔压力的大小;通过分析轴瓦出口边缘的流线稳定性,可验证油腔尺寸合适与否.     

液体静压转台倾斜油膜承载特性解析

针对CFD数值仿真计算过程中建模周期长、计算效率低的缺点,基于各封油边当量油膜厚度思想采用解析法来研究液体静压转台倾斜承载特性,推导了倾斜油膜承载力、弯矩和刚度的计算公式,提高了计算效率。利用CFD软件Fluent对油膜进行了数值仿真,结果表明倾斜油膜承载力误差保持在6%以内,弯矩误差保持在8%以内,验证了解析公式的可靠性。利用所提出的解析方法研究了倾斜位移率、供油压力、节流孔径和转速对油膜基本性能参数的影响规律。     

PM流量控制器参数对液体静压导轨性能影响的研究

在介绍PM流量控制器基本结构、工作原理以及流量压力特性基础上,推导出基于PM控制器的矩形对置油垫的承载能力、油膜刚度及动态传递函数的表达式。以某机床静压导轨的一对对置油垫为例,重点分析研究PM控制器的三个性能参数比流量cr、初始流量q0和泵压ps之间的相互关系及对油膜承载能力、静刚度及动态特性的影响。研究表明,给定初始流量q0和泵压ps,静刚度随cr增大而逐渐增加,在cr=6.2时静刚度有峰值,这对静压导轨的正常工作不利。比流量cr的合理取值范围为1.2～5.2,此时对置油垫静刚度随着q0的增大和pp减小而增大。基于油膜厚度传递函数表达式,研究敏感油路体积Vo=500 cm3时,在阶跃载荷作用下,不同的比流量cr、初始流量q0以及泵压ps对油膜在时域及频域内动态特性的影响。研究表明:在时域内,cr、q0、pp主要影响着油膜厚度的超调量,随着cr、q0增大以及泵压pp减小,其超调量明显增加。为提高油膜承载的稳定性,减小过渡过程的超调量,可减小cr、q0,增大泵压pp;在频域内,幅频特性曲线峰值处的频率为油液振动的固有频率。随着cr、q0的增加和pp减小,幅值越大,对应的固有频率也有所增大,失稳区频率范围变宽。当...     

小孔节流深浅腔动静压轴承承载特性解析研究

小孔节流深浅腔动静压轴承是一种采用小孔节流器实现节流作用及浅腔实现二次节流作用的动静压混合轴承。针对现有理论不能解析研究油腔结构参数及工作参数对承载特性影响规律的不足,以及计算流体力学数值仿真软件计算时周期长,而不便于工程设计人员应用的缺点,基于油腔压强分段线性化的思想,建立分析小孔节流深浅腔动静压轴承的油腔压强、承载能力、静刚度、进油流量及温升等承载特性的解析方法。进而以该方法研究动静压轴承的供油压强、主轴转速、进油孔径、浅腔深度、初始油膜厚度等参数对轴承承载特性的影响规律。研究发现,在其他结构参数及工作参数一定的条件下,浅腔深度为初始油膜厚度的2～3倍时,轴承刚度接近最大、温升接近最低。通过油腔压强的解析值与试验值的比较,证实了该方法的有效性和研究结果的正确性。     

困油压力对滑动轴承润滑状态的影响

为研究困油压力对轴承润滑状态的影响,在一个困油周期内,基于纯流体润滑状态设计要求,提出轴承-轴颈间所必需的承载量系数计算公式;依据泵样机参数,提出轴承-轴颈间所能提供的承载量系数的多项式拟合式;由所必需的承载量系数公式等于所能提供的承载量系数的定值优化方法,建立出困油压力与最小油膜厚度间的对应关系。通过一案例,对是否考虑困油压力的润滑状态计算结果进行比较和分析。案例分析结果表明:困油压力导致径向力增加45%～59%;导致最小油膜厚度降低19.6%～24.3%;困油压力造成轴承-轴颈间处于混合润滑状态,达不到原始的纯流体润滑状态设计要求。因此,困油压力对润滑状态影响较大,在泵轴设计中应充分考虑困油压力的影响,从而在结构上尽量缓解困油压力。     

基于有限差分法的径向滑动轴承油膜压力分布计算

滑动轴承广泛应用于旋转机械中,其静动态参数对旋转机械的运转有很大影响。确定滑动轴承的静动态参数依赖于轴承的油膜压力分布,Reynolds方程是油膜压力计算的基础。对于具体轴承参数计算,传统方法是利用已知的给定偏心率和宽径比下的轴承静动态参数进行曲线拟合,通过反推实际轴承的偏心率和偏位角,然后进行压力分布计算。这种逆运算不太方便。基于有限差分法,采用MATLAB软件编程计算,利用实际轴承已知外力和宽径比直接求解完整二维流动Reynolds方程得到油膜压力分布曲线,进一步利用改进方法设计计算实际轴承参数,取得较好的计算精度,使圆瓦轴承参数计算更为简便。     

The design of partially grooved externally pressurized bearings

Most hydrostatic and aerostatic bearings are designed using external restrictors in order to obtain sufficient bearing stiffness. Alternatives such as the shallow pocket or partially grooved externally pressurized bearing are seldom applied, in spite of their advantageous constructive simplicity. In this article a simple analytical model to analyze journal bearings with partially grooved surfaces is described. The results of the analytical model are compared to the results obtained by numerical analysis. Both incompressible and compressible fluids are considered. The formulas derived are of extreme simplicity and helpful in finding the groove dimensions for optimal load capability and calculating approximate bearing characteristics using a simple calculator.     

Theoretical Analysis and Numerical Simulation of the Static and Dynamic Characteristics of Hydrostatic Guides Based on Progressive Mengen Flow Controller

The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load,and this kind of hydrostatic guide is usually applied to the machine tools with moderate load.The static and dynamic characteristics of the guide have been studied by using some theoretical,numerical and experimental approaches,and some methods and measures have been proposed to improve its performances.The hydrostatic guide based on progressive mengen(PM) flow controller is especially suitable for the heavy numerical control(NC) machine tools.However,few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported.In this paper,the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing.On the basis of the analysis of hydrostatic bearing with circular pocket,some equations are derived for solving the static pressure,volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket.The function and the influencing factors of three pressures are clarified.The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived.With the help of software MATLAB,programs are coded with C++ language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller.The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide,and it should be reduced as small as possible when the field working condition is met.Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides.The research work has instructing significance for analyzing and designing the guide with PM flow controller.     

Theoretical and experimental investigations of a variable- impedance hydrodynamic bearing

The aim of the work described in this paper is to develop a hydrodynamic bearing whose oil film dynamic stiffness and damping coefficients could be tuned to take on low values, without upsetting the bearing steady load carrying capacity, in order to obtain an improved dynamic response for machines running in such bearings. It was required that this tuning of the bearing dynamic characteristics could be carried out after assembly of the machine in question, and if necessary while the machine was in operation.A theoretical analysis of the new design of bearing was carried out, based on a finite-difference model of the bearing oil film. This analysis enabled the steady-state load carrying capacity of the bearing to be calculated for any particular running conditions. The oil film stiffness and damping characteristics were then calculated using the finite-displacement technique; these were then used to calculate the unbalance response of a flexible rotor running in such bearings. Experimental measurements of the unbalance response of a model rotor running in the new bearing design were also recorded, and compared with similar measurements obtained when conventional bearings were used.Both theoretical and experimental results show that the proposed new bearing design has a similar steady load carrying capacity to that of conventional hydrodynamic bearings, but that the unbalanced response and force transmissibility of machines running in the new design of bearing are substantially superior to that obtained with conventional bearings.     

滚动轴承寿命计算中当量动载荷的确定

滚动轴承的寿命是衡量滚动轴承承载能力的重要指标。滚动轴承寿命计算的核心问题是当量动载荷的计算,而对不同类型的轴承当量动载荷计算的方法也不同。介绍了滚动轴承当量动载荷计算的一般过程和难点。