Thermohydrodynamic Analysis and Thermal Management of Spherical Spiral Groove Gas Bearings

A thermohydrodynamic model of spherical spiral groove bearings is presented by considering the effect of bearing temperature change on the material property of lubricant, gas flow characteristics in the grooves, and thermal energy transported in the entire bearing system. A gas mixing model in the grooves is introduced as the boundary condition to solve the bearing temperature distribution simultaneously with the heat conduction at the shaft and the housing. The bearing and rotor expansion caused by temperature increases, which is considerable compared to bearing clearance, is also examined. Prediction results show that the thermal expansion determined by actual bearing clearance has a crucial influence on the bearing load capacity. Manufacturing bearings with proper materials has significant effects on controlling thermal expansion effects on the bearing performance. The load capacity, which corresponds to the lubricant gas pressure, and gas suck flow rate have the same variation tendencies as the variation in groove depth and spiral angle. These similar tendencies have an opposite influence on the temperature and result in the temperature increase not being affected by the variation in grooves. However, varying the groove characteristics has a similar effect in carrying away the thermal energy as the variation in heat transfer coefficient, which could significantly control the temperature increase at the same time.     

复合材料水润滑艉轴承结构设计研究

基于ANSYS CFX流固耦合数值计算方法,对水润滑复合材料艉轴承的润滑性能及结构设计开展研究,阐述了不同水槽结构、间隙比、长径比、直径等对轴承承载力以及水膜压力、轴承变形量、最小水膜厚度、轴承摩擦因数的影响规律。并利用水润滑轴承试验台研究了不同水槽结构对轴承启动摩擦转矩、转变速度以及摩擦因数的影响。研究表明,轴承摩擦因数、水膜最大压强、轴承最大变形随水槽数增多而增大;轴承承载力、最小水膜厚度随间隙比增大而减小,随长径比增大而增大。总结了直径为100~500 mm、长径比为2~3、间隙比为0.1%~0.2%的水润滑艉轴承承载力的变化规律,为水润滑艉轴承设计提供一定的理论依据。     

均压槽与静压气体轴颈轴承承载特性的关系研究

主要研究通过开设不同结构形式的均压槽来提高静压气体轴颈轴承的承载能力和刚度,利用加权余量法和有限元离散化方法求解雷诺方程进行数值计算和仿真,针对单排孔和双排孔轴颈轴承,分析不同长度的周向均压槽,以及不同数量、不同位置和不同长度的轴向均压槽对轴承承载能力和刚度的影响规律。结果发现:开设周向均压槽和轴向均压槽都可以提高轴承的承载能力,相比开设周向均压槽,开设轴向均压槽对提高轴承的承载能力更为有效,而且只开设一条或两条轴向均压槽就能显著提高轴承的承载能力,通常将轴向均压槽置于气膜间隙较小的位置时能使轴承的承载能力和刚度最大。数值仿真结果通过试验进行验证,研究结果可用以指导高承载和高刚性静压气体轴颈轴承的设计。     

Stability of rigid rotor-aerostatic bearings with double compensations caused by orifice and inherence in series

This study elucidates the coupled effects of pressure compensation that is caused by orifice and inherence in series on static and dynamic characteristics of a rigid rotor that is supported by orifice-restricted aerostatic bearings. The load capacity and stability threshold are analyzed and compared to those obtained with separate orifice and inherence restrictions for various eccentricities, rotor speeds and restriction parameters and numbers of feeding holes. The simulation results have revealed clearly that the effects of orifice and inherence in series on bearing performance cannot be ignored in the design of aerostatic bearings.     

基于有限差分法的动压气体止推轴承静态特性分析

利用有限差分法对刚性表面和柔性表面两种动压气体轴承的无量纲控制方程进行分析求解,得到了两种轴承在理想支承条件下的压力分布,并由压力分布计算了承载力和摩擦力矩;分析了结构参数对两种轴承静态特性参数的影响.理论分析结果表明:相对于刚性表面气体止推轴承,柔性表面气体止推轴承平台区域的压力分布更加平缓;当柔度较小时,柔性表面动压气体轴承的承载力与刚性表面相当;选取适当的结构参数,可得到理论上的最大承载力以及较小的摩擦力矩.     

Effects of consistency variation of power law lubricants in squeeze films

The characteristics of squeeze film bearings with power law lubricants have been investigated by considering the effects of consistency variation. Various bearing geometries have been considered with rigid surfaces as well as with compliant layers. With stiff solids, a high consistency layer adjacent to the bearing surface increases the load capacity and time of squeezing and this increase is enhanced by the pseudoplastic behaviour of the lubricant. For squeeze film bearings with compliant layers, the film thickness increases with load, compliancy and conformity of the surfaces even with power law lubricants. It also increases with the consistency of the layer adjacent to the bearing surface.     

超临界二氧化碳涡轮机主轴静压轴承承载特性分析

以超临界CO2涡轮机主轴支承静压轴承为研究对象,基于Fluent软件建立静压轴承气膜的三维分析模型,分析了轴承结构、偏心率、气膜间隙对气膜压力、承载力和刚度的影响.结果表明:双排进气结构静压轴承的气膜压力、承载力和刚度均高于单排进气结构;偏心率对承载力有显著的影响,承载力和偏心率呈非线性正相关;在偏心率一定的条件下,平...     

The Performance of Externally Pressurized Bearings Using Simple Orifice Restrictors

The load capacity and vibration characteristics of externally pressurized thrust and journal bearings have been investigated. The bearings used orifices sufficiently recessed back from the bearing surface to ensure that the area of the orifice is the minimum presented to the gas flow. The journal bearings consist of plain cylinders with one or two rows of eight orifices, and the thrust plates of plain discs with six orifices drilled in equispaced circumferential grooves.

The load capacity of the thrust plates agrees with that calculated but the vibrations are greater than predicted. The load capacity of journal bearings is about half that calculated assuming axial flow conditions in the bearing, but circumferential flow can account for the difference. Synchronous and half-speed vibrations of a shaft rotating within these bearings have been measured and found to agree with those calculated on the assumption that the gas films behave as linear springs.     

油槽设计对滑动轴承泄油量的影响

为了确保支撑部位润滑良好,往往需要在轴或轴承表面设计各种油槽,然而增加油槽会伴随着泄油量的增加,影响其他零部件的润滑。为探讨油槽结构对滑动轴承泄油量的影响,采用不同的油槽结构设计方案设计3种齿轮滑动轴承。将轴承的总泄油分为油槽泄油和间隙泄油两部分,分别采用CFD仿真计算油槽泄油量,采用一维仿真计算间隙泄油量。基于某款轻型柴油机润滑系统的仿真试验,验证了计算方法的有效性。结果表明：无油槽的滑动轴承总泄油量最少,仅增加轴向油槽,轴承的总泄油量略有增加,同时增加轴向和周向油槽,轴承的总泄油量显著增加。对于润滑油总流量较低的轻型发动机,应合理设计滑动轴承的油槽结构,避免因泄油过多导致的润滑油压力不足问题。     

An Experimental Study on Film Pressure Circumferential Distribution of Water-Lubricated Rubber Bearings with Multiple Grooves

Experimental research on the water film pressure of water-lubricated rubber bearings with multiple grooves (WLRBMG) was carried out. A test rig was designed that could measure various performance of WLRBMG to further study the properties of the bearing. The experimental results indicated that film pressure circumferential distribution of WLRBMG was different from that of conventional rigid bearings. The relatively low water film pressure led to a partial contact between the shaft and rubber bearings, which will cause significant rubber deformation. Integration of the friction coefficient and orbit of the shaft center also suggest that the WLRBMG operated in mixed lubrication. The multigroove structure had a significant influence on the film pressure circumferential distribution of WLRBMG. By detailed analysis of the experimental results, some properties and working mechanism of the WLRBMG have been found and demonstrated.     

Load Capacity Estimation of Foil Air Journal Bearings for Oil-Free Turbomachinery Applications

This paper introduces a simple “Rule of Thumb” (ROT) method to estimate the load capacity of foil air journal bearings, which are self-acting compliant-surface hydrodynamic bearings being considered for Oil-Free turbomachinery applications such as gas turbine engines. The ROT is based on first principles and data available in the literature and it relates bearing load capacity to the bearing size and speed through an empirically based load capacity coefficient, D. It is shown that load capacity is a linear function of bearing surface velocity and bearing projected area. Furthermore, it was found that the load capacity coefficient, D, is related to the design features of the bearing compliant members and operating conditions (speed and ambient temperature). Early bearing designs with basic or “first generation” compliant support elements have relatively low load capacity. More advanced bearings, in which the compliance of the support structure is tailored, have load capacities up to five times those of simpler designs. The ROT enables simplified load capacity estimation for foil air journal bearings and can guide development of new Oil-Free turbomachinery systems.     

The dynamic behaviour of fluid bearings with grooved lands

In mechanical engineering, grooved mating lands are used for various reasons in a large number of bearing applications. This paper studies the effect of such grooves on the squeeze load characteristics, and hence on the damping capacity, of bearings. A comparison is given between the damping capacity of bearings with grooved lands and that of bearings with equivalent flat lands to give the same pressure flow characteristics. Different bearing configurations, representing thrust and journal applications, are analysed and discussed.     

变工况运行中结构参数对螺旋槽动压推力气体轴承承载力的影响

基于纳维-斯托克斯(N-S)方程建立了泵入型螺旋槽动压推力气体轴承仿真三维模型,分析了在变工况运行中不同的结构参数对螺旋槽动压气体推力轴承气膜承载力的影响,结果表明:槽深为30~50μm,螺旋角为18°~36°,台区轴承间隙为4~10μm,槽内径比为0.6~0.8,槽宽比为0.7~0.9,槽数为12~25时,该轴承的气膜承载力达到最大;轴承结构不同时,轴承的气膜承载力由大到小排序为凸型槽、平底槽、凹型槽,且泵入型大于泵出型。     

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.     

Abrasive jet machining for the microprofile control patterning of herringbone grooves

Fluid bearings have features of high speed and high rotation accuracy, and therefore, they are used in spindle motors of hard disk drives, cooling fans of central processing units, and other devices. Further, these bearings have microherringbone grooves on the shaft or sleeve inner surface that help generate dynamic pressure in the lubricant fluid around the shaft. Although the depth of the groove is constant, dynamic pressure can be increased by decreasing the depth from both ends to the central corner of each groove on a micron scale. This study aims to verify the effect of sloped herringbone grooves using computational fluid dynamics (CFD) analysis and to develop a new microfabrication method for manufacturing microsloped herringbone grooves on the shaft surface using abrasive jet machining. The generated dynamic pressure is analyzed using CFD; the results indicated that the sloped herringbone grooves result in an increase in the dynamic pressure at the groove tips and cause a decrease in the fluctuations in dynamic pressure in the circumferential direction.     

The Effect of Viscosity Variations with Temperature on the Performance of Spiral Groove Bearings

The load capacity and power loss of spiral groove bearings, lubricated with a Newtonian, incompressible liquid with a viscosity depending on temperature only, are determined by solving the continuity and momentum equations analytically and the energy equation for the grooves and ridges numerically. It is assumed that the total flow perpendicular to the relative velocity of the bearing parts is zero. This implies that the generated heat is discharged by conduction to the bearing parts only. The effect of the “thermal entrance region” is investigated.     

An analysis of the effect of journal bearings with helical grooves on the stability of a vertically mounted canned motor pump

An analysis of a vibration problem encountered on a vertically mounted, canned motor pump is described. Details are given of the flush water lubrication system and the two laminated pf resin journal bearings with helical grooves. The vibrational behaviour is described and attributed to bearing instability. A stability analysis based upon a finite element model of the rotor and finite difference solution to the bearing equations is discussed. Particular emphasis is given to the data available and the assumptions that had to be made. The role of the circumferential supply pressure in influencing stability id highlighted and the effect on stability and lubricant axial flow rate of the start of the start position and number of helical grooves is demonstrated. The effect of increased bearing clearance is also discussed. A recommendation to replace the single groove by a bearing with two grooves for the upper bearing is the main conclusion     

评价箔片径向空气轴承载荷性能的一种经验方法

介绍一种简单的“经验法则”来评价箔片空气轴承的载荷性能,它是一种可挠面的动压气体轴承,正在研究其在无油透平机械中的应用。经验法则是基于基本原理和文献中报道的可靠实验数据得出的,通过一个经验值——载荷系数D,将轴承的载荷性能和轴承的尺寸、速度联系起来。在经验法则中,轴承承载力是轴承转速和轴承设计面积的线性函数。轴承载荷系数D和轴承弹性支承结构的设计特点和轴承运行工况(温度、速度)有关。     

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.     

弹性箔片动压气体推力轴承承载性能研究

气弹耦合解是准确预测弹性箔片动压气体轴承承载性能的有效方法。通过引入箔片的弹性变形以及联立求解动压气体润滑Reynolds方程和弹性箔片的变形方程,给出了弹性箔片动压气体推力轴承的气弹耦合解。应用气弹耦合解理论,将顶层箔片的局部弹性变形纳入考虑范围,对弹性箔片动压气体推力轴承的承载性能进行了计算和分析。有限元数值仿真结果表明:顶层箔片在气膜压力作用下的局部弹性变形直接导致弹性箔片动压气体推力轴承承载能力的降低;根据轴承瓦块上气膜压力分布的特点合理设计支承拱箔的结构形式,可以减小顶层箔片的局部弹性变形,有效提高轴承的承载能力。得到了一种承载能力较高的弹性箔片动压气体推力轴承支承拱箔结构设计方案。