Performance characteristics of a capillary-compensated hydrostatic journal bearing

Results are presented of an extensive experimental investigation into the performance of a six-pocket hydrostatic journal bearing with pockets of non-uniform depth subjected to a range of static loads. Lubricating oil was supplied, at pressures of up to 8.957 MN m^?2 (1300 Ibf in^?2), to capillarytype restrictors, connected to the six pockets in the bearing. The bearing had an $\text{L}\text{D}$ ratio of unity and operated with a journal rotation ranging from zero to 2000 rev min^?1.The measured load capacity and the stiffness characteristics indicated that bearings of this type had a significant load capacity which was limited by the bending of the shaft. The load capacity increased with speed at low supply pressures, but decreased slightly with increasing speed at higher supply pressures. The stiffness increased with eccentricity ratio except at low supply pressures. Film pressure surveys aided the elucidation of some of the bearing performance characteristics.     

Dynamic characteristics of a hydrostatic journal bearing

The results of experimental investigations into the performance of a six-pocket hydrostatic journal bearing subjected to a range of dynamic loads are presented. The bearing performance was studied in terms of the load-carrying capacity and oil-film stiffness. The experimental results show that the test bearing has a better load-carrying capacity under dynamic load than under static load and that the load-carrying capacity and stiffness of the bearing are only limited by its mechanical strength.     

Performance analysis of a multirecess capillary compensated conical hydrostatic journal bearing

The present paper is aimed to study theoretically the performance of a 4-pocket hydrostatic conical journal bearing system. The Reynolds equation governing the flow of lubricant in the clearance space of bearing has been solved using FEM. The bearing static and dynamic performance characteristics have been presented for the values of external load W¯_r=0.1-1.0 and for the semi cone angles (γ=10°, 20°, 30° and 40°). The numerically simulated results indicate that the lubricant flow rate is significantly reduced in case of conical journal bearing vis a vis the corresponding similar circular hydrostatic journal bearing.     

Static and dynamic performance characteristics of an orifice compensated hydrostatic journal bearing with non-Newtonian lubricants

This paper presents a theoretical study of the performance characteristics of hydrostatic rigid orifice compensated multirecess journal bearings using non-Newtonian lubricants. The generalized Reynolds equation governing the flow of lubricant having variable viscosity has been solved using the finite element method and iterative procedure. The static and dynamic performance characteristics are presented for non-Newtonian lubricants of which constitutive equation has been represented by the cubic shear stress law. The non-linearity factor () in the cubic shear stress law significantly influences the bearing performance characteristics, particularly the dynamic characteristics.     

Load capacity and stiffness of misaligned hydrostatic recessed journal bearings

The effects of journal misalignment on the static properties of capillarycompensated hydrostatic journal bearings are investigated theoretically. It is demonstrated that misalignment reduces the stiffness as well as the load capacity and that the amounts of reduction are substantial when the value of the slope δ is greater than 0.2. The results of the analysis are applied to bearings with any number of recesses. Good agreement between theoretical and experimental results for the loci of the shaft centre and the stiffness is obtained.     

Performance characteristics of hydrostatic journal bearings with journal rotation by a finite element method

Theoretical studies have been made of a capillary-compensated hydrostatic oil journal bearing supporting a rotating spindle, using a finite element method. Performance data are developed for a four-pocket bearing of $\text{L}\text{D}\text{= 1.0}$. Stiffness and load capacity curves for two significant directions of the line of centres are given for various design parameters and eccentricity ratios. The effects of rotation and the feeding system on the stiffness, load capacity, flow and attitude angle are discussed.     

Load capacity of multi-recess hydrostatic journal bearings at high eccentricities

A finite element program has been set up to evaluate the pocket pressure, load capacity and the rate of flow of the lubricant in a four pocket hydrostatic journal bearing under stationary as well as steady speed conditions. Numerical calculations have been extended to the extreme journal position which represents the eccentricity ratio close to unity. Also experimental measurements have been carried out for the particular case of a stationary journal and the results thus obtained have been compared with those numerically obtained. While confirming the previously predicted load capacity at low eccentricity ratios, the present numerical and experimental results show a higher load capacity at high eccentricity ratios close to unity.     

不同流态下高速动静压径向轴承静特性研究

针对深浅腔动静压径向轴承建立了层流、紊流共存时的油膜数学模型,采用有限元法计算了油膜的静态特性,并与完全层流和完全紊流两种状态下的计算结果进行了比较.结论表明:除流量外,静特性参数紊流工况下最大,混合流态次之,层流最小.     

变频恒流静压轴承的研制

在恒流静压轴承系统中,引入了温度、压力、流量反馈,数据处理系统通过PLC控制交流变频电动机来调节静压轴承静压油流量,处于最佳状态时锁定。此轴承很好地解决了我们研制的DL250数控重型卧式镗车床静压轴承重载高精度的难题。     

Performance analysis of flexible multirecess hydrostatic journal bearing operating with micropolar lubricant

This paper presents the analytical study of the effect of the bearing shell flexibility on the performance of multirecess hydrostatic journal bearing system operating with micropolar lubricant. The modified Reynolds equation for the flow of micropolar lubricant through constant flow valve‐compensated hydrostatic journal bearing has been solved by finite element technique based on Galerkins method, and the resulting elastic deformation in the bearing shell due to fluid‐film pressure has been determined iteratively, in which the deformation coefficient accounts for the bearing shell flexibility. The computed results suggest that the influence of the micropolar effect on bearing performance characteristics is significantly affected by the bearing shell flexibility. Copyright © 2012 John Wiley & Sons, Ltd.     

Study on mixing flow effects in a high-speed journal bearing

The influence of turbulence on journal bearing operation is examined. The thermal variability is studied for isothermal, convective and adiabatic conditions on the walls under aligned and misaligned conditions. Also, a contraction ratio at the cavitation region and the mixing between re-circulating oil and inlet oil are included. An algorithm for the solution of the coupled turbulent Reynolds and energy equations is used to examine the effects of the various factors. Heat convection is found to play but a small role in determining friction and load under no mixing condition. However, under realistic mixing condition, the heat convection may not be ignored. The wall temperature and heat transfer have been found to be of secondary importance to the mixing effectiveness at the groove and the final mixture temperature.     

Performance characteristics for the hydrostatic thrust bearing of a saw blade

A semi-analytical solution is presented to obtain the pressure distribution, the load capacity, the frictional moment and the lubricant flow rate for a laminar flow, hydrostatic bearing with its axis offset from thee axis of the saw blade. The general equations are developed and solved for a variable film thickness due to plate vibrations. It was found that the load, friction and lubricant flow rate are strong functions of film thickness variations , bearing number λ and the bearing offset from the rotation axis     

Dynamic characteristics and stability of a journal bearing in a non-laminar lubrication regime

A mathematical model to determine the stiffness and damping coefficients and the stability limit curves of a journal bearing in a non-laminar lubrication regime is described. The results show the flow regime influence on the dynamic characteristics of cylindrical bearings and on the stability of a rigid rotor on rigid supports.     

Performance characteristics of tilted three-lobe journal bearing configurations

A tilted three-lobe journal bearing is a geometric variation of the usual symmetric three-lobe configuration. This investigation of the performance characteristics of the three-lobe configurations over a wide range of tilt angles shows that, within a specific range of tilt angles, the tilted configurations exhibit superior dynamic performance to the usual symmetric three-lobe bearing.     

重型静压轴承流场与压力场仿真分析

采用FLUENT软件对重型恒流静压轴承油膜的三维压力分布及流场分布进行了数值分析,重点分析进出口区域的流速,并研究了出口压力与流速变化趋势.分析结果表明,流场进口附近流速变化剧烈,但是整体流动呈现很强的规律性.油膜整体压力场成均匀对称分布,不受出口位置影响.为进一步研究重型静压轴承的性能与设计提供理论依据.     

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。     

A study of slot-entry hydrostatic/hybrid journal bearing using the finite element method

A theoretical study concerning the static and dynamic performance of hydrostatic/hybrid journal bearing compensated by slot restrictor has been presented using the finite element method (FEM). Results have been presented for a double row symmetric as well as asymmetric configurations for different values of slot width ratios (SWR) and external load ( ). In order to have a better understanding of their performance vis-à-vis other non-recessed bearing configurations, the performance characteristics of slot-entry journal bearings have been compared with that of similar hole-entry compensated journal bearings using capillary, orifice and constant flow valve restrictors for the same bearing geometric and operating parameters. The comparative study indicates that asymmetric slot-entry journal bearings provide an improved stability threshold speed margin compared with asymmetric hole entry journal bearings compensated by capillary, orifice and constant flow valve restrictors.     

Steady state and stability characteristics of a hydrodynamic journal bearing with a non-Newtonian lubricant

The effect of the non-Newtonian behaviour of lubricants, resulting from the addition of polymers, on the performance of hydrodynamic journal bearings was investigated. An empirical fluid flow equation which adequately represents the flow behaviour of lubricant was used to obtain a modified form of Reynolds' equation. Finite difference numerical solutions were obtained for steady state conditions at various width-to-diameter ratios. The results show a strong influence of the width-to-diameter ratio on the load capacity of journal bearings. Linearised stiffness and damping coefficients were evaluated from the fluid film force equations for the unsteady motion of the journal centre and were used to predict the stability limits of a simple rigid rotor-bearing system which showed a reduction in threshold speeds. The steady state load capacity and stability limits were verified experimentally for finite width bearings.