基于匀压和阻尼的空气静压轴承静态特性研究*

针对常规空气静压轴承设计时存在的承载能力、刚度与气动锤之间的矛盾,提出一种基于虚拟均压和被动阻尼设计方法。采用该方法设计一种含环布均压槽和阵列阻尼孔的矩形平面空气静压止推轴承,并研究其静态特性。研究结果表明：与常规空气静压轴承结构相比,设计的空气静压止推轴承在供气压力0.5 MPa下的最高承载力提高了43.4%,最高刚度提高了51.3%;减小阻尼孔数量、减小节流孔径、提高供气压力和增设均压槽可获得最佳刚度特性;增加阻尼孔数量、减小节流孔径、提高供气压力和增设均压槽可获得最佳静态特性和动态稳定特性的综合性能。     

Design of annular recess hydrostatic thrust bearing under dynamic loading

Design charts are presented of a dynamically loaded thrust bearing with as annular recess. The effect of non-parallelism between the bearing and the runner surfaces is also considered, since this is a common problem in hydrostatic thrust bearings. Based on pre-assigned dynamic excitations the pressure equation is solved numerically by finite difference methods to render the bearing performance characteristics namely: load capacity; bearing stiffness; damping coefficient; and lubricant flow rate. Results concluded that the bearing performance chareacteristics are dependent on the bearing radii ratios, the squeeze number, the bearing number and the tilt parameter.     

Determination of Optimum Proportions for Hydrostatic Bearings

The effect of recess size on the pressure, flow and power requirements of several hydrostatic bearing configurations is described in terms of dimensionless coefficients called performance factors. Performance factors are determined analytically for a circular hydrostatic thrust bearing with a circular recess (for which there is a known solution), compared graphically with the electric analog solutions for this bearing and found to be in excellent agreement. The electric analog approach is also used to determine the performance factors of several other bearing configurations for which there are no known solutions. These data are presented in the form of dimensionless curves. It was found that for a given bearing configuration, there is a particular recess size which will give minimum supply pump power. Where limiting factors, such as, pump output pressure and/or flow do not dominate, it is suggested that bearings be designed to operate at the minimum pump power point.     

Performance of Hydrostatic Textured Thrust Bearing with Supply Holes Operating with Non-Newtonian Lubricant

The present article proposes a technique to improve the performance of textured hydrostatic thrust bearings with the use of oil supply holes. The article provides a comparison between smooth and surface-textured hydrostatic thrust bearings. To get an accurate prediction of the caviation regime, the Jakobsson-Floberg-Olsson (JFO) mass conservation algorithm has been used instead of the Reynolds boundary conditions. It has been observed that surface texture results in a significant decrease in friction power loss along with an improvement in other performance parameters. The study also reveals that the location of the supply hole for the lubricant system significantly affects the bearing performance.     

An isoviscous,isothermal model investigating the influence of hydrostatic recesses on a spring-supported tilting pad thrust bearing

Tilting-pad hydrodynamic thrust bearings are used in hydroelectric power stations around the world, reliably supporting turbines weighing hundreds of tonnes, over decades of service. Newer designs incorporate hydrostatic recesses machined into the sector-shaped pads.With the aid of external oil pressurisation at low rotational speeds, oil film thickness is increased, thereby reducing friction and wear to the benefit of service life and reliability. It follows that older generating plants, lacking such assistance, stand to benefit from being retrofitted with hydrostatic lubrication systems. The design process is not trivial however – the need to increase the groove area to permit spontaneous lifting of the turbine under hydrostatic operation conflicts with the need to preserve performance of the original plane pad design. A haphazardly designed recess can change the pressure distribution of the oil film in such a way as to tilt the pad away from its optimum position. This may lead to reduced oil film thickness and increased temperature, which is concomitant with reduced mechanical efficiency and increased risk of damage to the bearing surfaces. It is therefore, inadvisable to ignore the presence of grooves in simulations. In this work, a numerical study of a sector-shaped pad is undertaken to understand how recess size and shape can affect the performance of a typical bearing. An isoviscous, isothermal model has been used in this instance because the operating conditions of the turbine in question were shown not to be severe enough to warrant the computational expense of a fully coupled thermoelastic hydrodynamic model.     

On the application of Rabinowitsch fluid model on an annular ring hydrostatic thrust bearing

Present theoretical analysis investigates the effects of centrifugal inertia on the performance of annular ring hydrostatic thrust bearings lubricated with non-Newtonian pseudoplastic lubricants—Rabinowitsch fluid model. Solution for pressure distribution has been obtained in the analysis. The influence of centrifugal inertia in the recess region is also considered by taking non-constant recess pressure. The load capacity and flow rate have been calculated numerically for various values of pseudoplastic parameter. In the limiting case in which there is an absence of pseudoplasticity, the results are compared with the pre-established results of Newtonian lubricants and found in good agreement.     

水润滑动静压轴承三维压力及温度场分布理论研究

以4腔、毛细节流形式下的深腔动静压轴承为研究对象,采用有限差分数值方法求解了广义雷诺方程,该过程考虑了紊流、粘度和密度随压力及温度变化的影响。研究得到了在水介质润滑下的动静压轴承三维压力分布、温度场分布及动特性系数。结果表明在高速高压水润滑条件下的动静压轴承表现出了与粘度较大的油润滑条件下不同的液腔压力分布、温度分布等特性。水润滑轴承第3和第4个液腔压力较大,第1个液腔主要用来增加其稳定性,而同等条件下的油润滑轴承第2和第3个油腔压力较大,第4个液腔增加其稳定性。相比油润滑轴承,水润滑轴承温升较高,因此对于低粘度介质润滑下的轴承性能研究需要考虑温升影响。     

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。     

Influence of recess shape on the performance of a capillary compensated circular thrust pad hydrostatic bearing

This work describes a theoretical study concerning the static and dynamic performance of a circular thrust pad hydrostatic bearing having recesses of different geometric shapes. The Finite Element Method has been used to compute the performance characteristics of a circular thrust pad hydrostatic bearing with circular, rectangular, elliptical and annular recesses. The performance has been compared on the basis of the same bearing operating and the same geometric parameters, i.e. the same ratio of bearing to pocket area ( ) and the same value of restrictor design parameter . Further, a comparative study of the various bearing configurations has been carried out vis-à-vis different compensating devices such as capillary, orifice, and constant flow valve restrictors so as to study the combined influence of the geometric shape of recesses and the compensating device on bearing performance. The computed results indicate that to get an improved performance from a hydrostatic circular thrust pad bearing, a proper selection of the geometric shape of the recess in conjunction with the type of restrictor and the value of the restrictor design parameter is essential.     

可控节流参数对液体静压轴承特性的影响研究

节流器是液体静压主轴的核心元件,其节流特性对液体静压主轴的刚度和回转精度具有直接影响。针对现有节流器在主轴工作时节流特性不可控的不足,提出一款预压预调型可控节流器。在分析可控节流器工作原理和节流特性基础上,根据流体润滑理论,建立基于可控节流器的液体静压轴承承载性能的理论模型,研究可控节流器供油压力、弹簧刚度和控制油腔压力等参数对液体静压轴承承载性能的影响规律,并与固定节流液体静压轴承的承载性能进行对比。研究发现,在其他结构参数及工作参数一定的条件下,可控节流器能够显著地提高液体静压轴承的油膜刚度;在不同偏心率条件下,可控节流液体静压轴承的最佳油膜刚度对应的节流参数不同。在开发的液体静压电主轴试验台上进行了试验研究,通过对油腔压力和油膜刚度的理论计算值与试验测量值的对比,证实了可控节流方案的有效性。     

不同压力腔的气体静压轴承静特性的数值模拟

气体静压轴承以其低摩擦、高精度成功应用于高精密回转运动台,其定位精度已达到纳米级水平,达到了物理极限,因此压力腔形状对气体静压轴承的影响无法忽略。通过CFD数值模拟,研究了不同压力腔形状对气体静压轴承静态性能的影响。针对矩形压力腔、圆形压力腔和锥形压力腔,研究分析了气膜内压力分布、气体质量流量和承载力等静态性能。结果表明:相同的条件下,锥形压力腔承载力较大,且压力腔内部气旋强度较弱,比较适合应用于高压重载的场合。     

涡旋式制冷压缩机止推轴承润滑性能研究的最新进展

在涡旋式制冷压缩机运行过程中,止推轴承动止推盘两端的压力差对轴承的润滑性能有显著的影响;止推轴承本身的结构特点,如键槽的存在,也会影响止推间隙的压力分布以及倾斜角,从而影响止推轴承的润滑性能.对止推轴承动止推盘两端的压力差、止推轴承本身结构等影响因素从理论或试验等方面进行探讨,并对将来涡旋式制冷压缩机止推轴承润滑性能的研究进行展望.     

静压向心轴承的结构创新设计

为提高矩形油腔静压向心轴承工作时产生的动压效应，设计了一种含矩形油腔、“门形”油腔和“回形”油腔的复合式油腔结构的新型静压向心轴承，该结构轴承在产生足够的静压承载能力的基础上可产生很强的动压效应。经理论分析与实验表明，复合式油腔静压向心轴承的承载能力和油膜刚度较常规使用的矩形油腔静压向心轴承均有大幅度提高。轴承的偏心率可由截流器无级调节。     

Static and dynamic characteristics of externally pressurized circular step thrust bearings lubricated with couple stress fluids

The combined effects of couple stresses, fluid inertia and recess volume fluid compressibility on the steady-state performance and the dynamic stiffness and damping characteristics of hydrostatic circular step thrust bearings are presented theoretically. Based on the micro-continuum theory, the modified Reynolds equation and the recess flow continuity equation are derived by using the Stokes constitutive equations to account for the couple stress effect resulting from a lubricant blended with various additives. Using a perturbation technique, results in terms of steady-state load-carrying capacity, oil flow rate, stiffness and damping coefficients are presented. A design example is also illustrated for engineering and industrial applications.     

Nanosys-1000机床静压止推轴承流场分布规律及承载特性

为了提高Nanosys-1000非球面曲面光学零件超精密加工机床加工精度,研究了机床核心部件静压止推轴承内流场分布规律,进而揭示其承载特性。利用ANSYS/Fluent软件建立对称结构静压止推轴承扇形油垫的仿真模型,采用层流模式对进油压力为1.3~1.9 MPa、油膜厚度为20~36 μm的油垫流场分布规律与承载特性进行分析。研究结果表明：油垫内压力在油腔区域比较均匀,沿封油边呈线性下降;油膜承载力随油腔压力线性增长,且在同一进油压力下,油膜厚度越小,油膜承载力越大,进油压力为1.5 MPa时,油膜厚度从36 μm减小到20 μm,油腔压力从3.05×10⁵ Pa增加到8.02×10⁵ Pa,油膜承载力相应地从880 N增加到2 109 N;同一负载即油膜承载力下,进油压力越高,油膜厚度越大,油膜承载力为1 320 N时,进油压力从1.3 MPa增加到1.9 MPa,油膜厚度从26 μm增加到30 μm;同一油膜厚度下,进油压力越高,润滑油流量越大,油膜厚度为28 μm时,进油压力从1.3 MPa增加到1.9 MPa,润滑油流量从0.179 L/min增加到0.231 L/min。相关研究结果在研制的Nanosys-1000非球面曲面超精密加工机床静压止推轴承上得到了验证。     

The Behavior of the Centrally Pivoted Thrust Bearing Pad with Hydrostatic Recesses Pressurized by a Constant-Rate Flow

The tilting behavior of the centrally pivoted, externally pressurized tilting thrust pad is investigated. The pressure distribution in the oil film is obtained by solving the Reynolds' equation which takes into account the external pressurization induced by a constant-rate flow. The relation between the size of the hydrostatic recess and the tilt angle of the pad is described. Calculations show that a pad with pressure recesses may have a negative tilt angle, depending on the size of the recess. The pressure variation around the hydrostatic pressure recess causes the moment to force the pad to tilt backward. At high shaft rotational speeds, the pad tilts backward too much and eventually fails to support the load. The hydrostatic pressure recess that is utilized to avoid the metal contact may cause this. The result was confirmed by experiments.     

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。     

Performance of membrane compensated multirecess hydrostatic/hybrid flexible journal bearing system considering various recess shapes

The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane flow valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an elliptical recessed bearing and a triangular recessed bearing. The equation governing the flow of lubricant in a journal bearing together with 3D elasticity equation and restrictor flow equation are solved by using the Finite Element Method. The study describes the effect of recess shape, bearing flexibility and a method of compensation on the performance characteristics of a hydrostatic/hybrid journal bearing system. A comparative performance of the membrane compensated hydrostatic/hybrid journal bearing system has also been studied vis-à-vis capillary, orifice and constant flow valve restrictors. The results presented in this study amply demonstrate that the shape of recess/pocket of a hydrostatic/hybrid flexible journal bearing system affects the performance of the bearing quite appreciably and a proper selection of recess shape along with a suitable compensating device is needed to get an improved performance from the bearing.     

Stability of multilobe hybrid bearing with short sills—part II

A small amplitude perturbation analysis has been carried out to determine the rotordynamic characteristics of multilobe hybrid bearings with short axial and circumferential sills. Unsteady state recess flow continuity equation has been written for orifice compensated bearing in terms of dynamic recess pressures by perturbing steady state flow equation. Dynamic recess pressures are evaluated by solving unsteady recess flow continuity equations to determine the dynamic load capacity of the bearing. Stiffness and damping coefficients of the bearing are determined from the dynamic load capacity of the bearing. Results of dynamic characteristics of three lobe and four lobe hybrid bearings are presented for various offset factors, speed, concentric pressure and eccentricity ratios. Multilobe hybrid bearings with offset factors more than one are found to exhibit better dynamic behaviour than circular hybrid bearings.     

变黏度静压滑动轴承高速时油膜动态润滑特性

静压滑动轴承转台直径大（D=4.5 m）,高转速运行时产生线速度值很大,其内部润滑油膜受压及剪切发热导致油膜变薄进而影响到机床加工精度和运行可靠性。针对新型Q1-205双矩形腔静压推力轴承,采用动网格技术探索变黏度条件静压轴承高速时的油膜动态润滑特性。建立该静压轴承的流量、承载力、油膜温升等理论模型,自定义用于控制边界层网格运动及变黏度的UDF程序,选取外载荷12 t,转速为80~200 r/min（线速度18~48 m/s）高速下的工况条件参数进行动态润滑特性数值模拟,并进行相同工况参数下的试验验证,揭示出高速时油膜厚度变化对油膜温度、油腔压力、封油边处流量的影响规律。研究发现,该型号轴承在承载12 t时,随着膜厚的减小,油膜剪切发热严重,温升加剧,且高速下受润滑油黏度变化影响造成压力损失严重,研究数据为工程上静压轴承可靠运行提供理论依据。