Investigations on a Magnetic-Hydrodynamic Hybrid Thrust Bearing

In the present work, a magnetic-hydrodynamic hybrid thrust bearing is investigated. The force of the bearing comes from the hydrodynamic film and magnetic field. This paper studies a model of the bearing force and develops an experimental rig to investigate the thrust bearing. Predictions from the model are compared with measured data from the experimental rig.     

磁动压混合推力轴承的研究

提出了一种利用磁场力辅助流体动压轴承工作的磁动压混合推力轴承。这种轴承在机器起动和停车阶段,依靠磁场力支承转子系统,当机器达到一定转速后,主要由动压油膜承受轴上载荷,从而克服了流体动压轴承在此阶段出现混合摩擦的问题。研究了这种混合推力轴承承载能力的数学模型,计算了磁轴承的承载能力。设计制造了试验装置并对这种轴承在不同气隙和转速下的性能进行了试验测试。结果表明这种磁动压混合的工作原理是可行的,可以改善流体动压轴承的工作性能。     

尺寸误差对转子系统摩擦功率的影响

针对滑动轴承转子系统存在的尺寸误差,建立了非线性油膜力模型,着重研究了滑动轴承与轴颈直径误差及其交互作用对系统动力学特性、承载能力和稳定性的影响,并利用稳定性临界转速对应的偏心率,定量分析了偏心率对滑动轴承转子系统摩擦功率损失的影响。图形曲线分析表明,各种尺寸变化对系统会产生不同程度的影响,摩擦功率随着偏心率的增大而减小,当偏心率在0.6948附近时摩擦功率达到最小。研究结果为减小系统功耗、合理设计系统参数提供了可靠的依据。     

表面织构动压滑动轴承油膜力解析模型

提出一种求解表面织构动压轴承油膜力的解析模型。基于Sommerfeld油膜边界,通过分离变量的方法,求解表面织构动压滑动轴承二阶偏微分Reynolds方程,得到表面织构动压滑动轴承油膜压力解析式。以圆形凹坑轴承为例,在油膜区域通过积分求得织构轴承的油膜力,分析织构参数对油膜压力的影响,研究发现,表面织构位于收敛区域(升压区)的轴承,其润滑与承载性能优于表面织构位于发散区域(降压区)的轴承、全织构轴承以及光滑轴承。对比了提出的解析模型与FDM和CFD模型在不同长径比和偏心率下的计算结果,结果表明,提出的解析模型能准确地描述表面织构动压滑动轴承的油膜力,且计算结果同FDM和CFD模型计算结果基本一致,验证了该模型的正确性。     

Dynamic Friction Model of Lubricated Surfaces for Precise Motion Control

A model is developed to describe dynamic friction effects in lubricated surfaces. The model covers the hydrodynamic, mixed and boundary lubrication regions. The dynamic friction model can predict the friction force for time-varying velocity, and is useful in precise motion control. The model presented is for a short journal bearing, but can be extended to other geometries of sliding surfaces, such as point and line contacts or rolling element bearings. The friction is related to a time variable fluid film thickness, resulting from journal vibrations relative to the sleeve. The proposed model agrees qualitatively with experimental results for lubricated line contact. Both show similar hysteresis-type friction curves under oscillating velocity.     

椭圆度对椭圆滑动轴承稳定性的影响

建立了椭圆滑动轴承的油膜力力学模型,并采用基于Sommerfeld数的滑动轴承转子系统稳定性分析方法分析了该模型。利用量纲一运行参数up得到不同椭圆度误差的滑动轴承的稳定性临界曲线。结果表明：滑动轴承轴颈的椭圆度误差对滑动轴承转子系统有显著影响。     

油水混合对径向滑动轴承润滑性能的影响

基于流体动压润滑基础理论,利用数值计算方法,在MATLAB软件中建立径向滑动轴承油水混合动压润滑的数学模型,对比分析润滑油中不同含水量对径向滑动轴承润滑性能的影响。结果表明:润滑油中混入少量的水对滑动轴承液膜的厚度和压力产生了一定的影响,最小液膜厚度随含水量的增加而减小,最大液膜压力随含水量的增加而增加;润滑油中混入少量水使得液膜合力和摩擦力变大,将不利于轴承的动压润滑,从而导致轴承润滑性能变差,并且加大轴承的摩擦磨损,降低径向滑动轴承的使用寿命。     

永磁体形性特征对磁水复合支撑式艉轴承润滑特性的影响

螺旋桨重力会导致船舶推进轴系发生挠曲,造成艉轴承边缘润滑状态恶劣。采用一种磁水复合支撑形式的艉轴承,通过引入永磁体磁力作用,改善桨重因素对艉轴承边缘润滑状态的不利影响;构建永磁体三维磁力特性分析方法,探究不同永磁体材料磁性质和布置形式对磁力承载性能的影响规律;基于艉轴承弹性流体动压润滑分析方法,获取永磁体形性特征对润滑特性的影响规律。结果表明：磁承载力受永磁体材料剩磁的影响明显,材料剩磁越大,永磁体承载力越大,轴承润滑状态相对越好;沿周向增加磁块数目或增加永磁块轴向长度可以增大永磁体的承载力,但永磁体承载效率可能下降,设计时需综合考虑;磁体的布置形式也对磁力承载性能和润滑性能影响显著,在永磁体体积相同的情况下,更为合理的布置形式可使永磁体承载力与艉轴承最小水膜厚度明显增大。     

Different Magnetic Models in the Design of Hydrodynamic Journal Bearings Lubricated with Non-Newtonian Ferrofluid

This work is concerned with theoretical study of hydrodynamic journal bearings lubricated with ferrofluids exhibiting non-Newtonian behavior. Based on the momentum and continuity equations for ferrofluid under an applied magnetic field, a modified Reynolds equation has been obtained. Assuming linear behavior for the magnetic material of the ferrofluid, the magnetic force was calculated. The Reynolds equation has been derived to be able to apply to any magnetic field distribution model. Using different magnetic field models, the equation has been solved numerically by the finite-difference technique with appropriate iterative technique and pressure distributions have been obtained. The boundary shape of the load-carrying active regions (positive-pressure regions) and cavitation regions (zero-pressure regions) could be then determined. The solution renders the bearing performance characteristics, namely: load-carrying capacity, attitude angle of the journal center, frictional force at the journal surface, friction coefficient and bearing side leakage. The results indicated that the flow-behavior index has a large effect on the bearing performance. When the bearing operates at high eccentricity ratios, the increase of flow-behavior index gives higher load capacity, lower attitude angle, higher frictional force, lower friction coefficient and higher side leakage. At low eccentricity ratios where the magnetic effects are significant, the effect of the flow-behavior index depends mainly on the magnetic field distribution model used.     

On the vibration of rotor-bearing system with squeeze film damper in an energy storage flywheel

The permanent magnetic bearing and the small-sized hydrodynamic spiral groove bearing are utilized as supports for the rotor of the energy storage flywheel system. The hydrodynamic bearing and the squeeze film damper do not need the oil cycle to remove the heat caused by friction because the friction loss is small. The linear dynamics model with four degrees of freedom is built to describe the vibration of the flywheel rotor-bearing system. The squeeze film dampers show good behavior in suppressing the vibration and improving the stability of the rotor-bearing system. The analytical solution of the dynamic characteristic coefficients of the squeeze film is achieved from Reynolds equation after some simplifications are taken. The numerical computation shows that the moment unbalance excites larger vibration of the rotor than the force unbalance. The upper damper plays an important role in helping the rotor pass its critical speed. The damping coefficient of the squeeze film dampers should be selected carefully. The flywheel arrived at the speed of 39,000 rpm and stored the energy of 308 Wh in the experiment. The calculated unbalance response is compared to the test response of the rotor storing quantities of kinetic energy. The comparison indicates that the dynamics model of the rotor-bearing-damper system is appropriate.     

Journal bearing performance under starved lubrication

The hydrodynamic performance of a journal bearing under starved lubrication conditions is studied theoretically and experimentally. When lubricant is supplied to a journal bearing from an oil groove at an insufficient oil flow rate, the hydrodynamic oil film cannot cover the full width of the bearing at the inlet of the convergent bearing clearance, and the covered width increases gradually with the decrease in film thickness in the circumferential direction. This phenomenon affects the static and dynamic performance of the journal bearing. The oil film boundary in the bearing clearance is calculated numerically for a constant load and a constant speed under the assumption of laminar, iso-viscous lubrication. Measurements are in good agreement with predictions. Some more calculations of journal centre loci are given.     

磁流体润滑滑动轴承的研制和性能研究

研制了磁流体润滑滑动轴承 ,建立了磁流体滑动轴承试验装置。对磁流体滑动轴承和传统滑动轴承进行了对比试验研究。通过大量试验的测试结果分析比较 ,发现磁流体滑动轴承能形成良好的全油膜润滑 ,产生的摩擦力比传统滑动轴承要小得多 ,因此推断出磁流体滑动轴承的承载能力和抗磨损能力大于同等条件下的传统滑动轴承。     

On the dynamic loading of gear teeth as affected by journal motion in a hydrodynamic bearing-rotor-gear pair system

The paper is an attempt to include the effect of journal motion and the oil film forces on the determination of dynamic gear tooth loading in a hydrodynamic bearing-rotor-gear pair system. A mathematical model has been developed which relates dynamic loads on the teeth of an involute spur gear pair to the instantaneous state of the pinion journal centre in the oil film space and various bearing parameters. The direction of instantaneous line of action is determined from kinematic considerations. effects of both the full-film (360 degrees) and the cavitated π-film models of the journal bearing are used to arrive at the aforementioned relationships. Dynamic loads on gear teeth as well as on bearing film have been calculated when the journal traces certain specified paths in the clearance space. Some of the results emphasize the importance of coupling gear analysis with bearing analysis.     

Numeric and experimental study of generalized geometrical design of a hydrodynamic journal bearing based on the general film thickness equation

This paper deals with multi-objective shape optimization related to the geometrical design of a hydrodynamic journal bearing. The aim proposed here is to show that optimum shape design with better performance could surpass the limitations of existing bearing profiles. Attempting to remove the difficulty of selecting the weighting factor in multi-objective journal bearing optimization problems, a modified non-dominant sort in genetic algorithm was used as an optimization tool with a penalty to those solutions that violate constraints. Three kinds of optimized shapes were manufactured and taken as experimental objects. Experimental apparatus was described and some experimental data was presented. The comparison was made for the optimized bearings between numeric values and experimental data. The results show that the new method for shape optimization of hydrodynamic journal bearings based on the general film thickness equation is feasible.     

转子偏斜角不对中对滑动轴承系统运行稳定性的影响

为了进一步了解转子偏斜角误差对滑动轴承系统运行稳定性的影响,建立了带有转子偏斜角误差的滑动轴承系统动力学模型,研究了不同程度的转子偏斜角误差对滑动轴承油膜厚度分布、油膜压力场的分布、系统承载能力、工作运行稳定性以及轴颈摩擦功率损耗的影响.其结果表明,转子偏斜角误差的存在将会对油膜厚度分布和油膜压力场分布产生显著的影响;...     

A Method for the Measurement of Hydrodynamic Oil Films Using Ultrasonic Reflection

The measurement of the thickness of an oil film in a lubricated component is essential information for performance monitoring and control. In this work, a new method for oil film thickness measurement, based on the reflection of ultrasound, is evaluated for use in fluid film journal bearing applications. An ultrasonic wave will be partially reflected when it strikes a thin layer between two solid media. The proportion of the wave reflected depends on the thickness of the layer and its acoustic properties. A simple quasi-static spring model shows how the reflection depends on the stiffness of the layer alone. This method has been first evaluated using flat plates separated by a film of oil, and then used in the measurement of oil films in a hydrodynamic journal bearing. A transducer is mounted on the outside of the journal and a pulse propagated through the shell. The pulse is reflected back at the oil film and received by the same transducer. The amplitude of the reflected wave is processed in the frequency domain. The spring model is then used to determine the oil film stiffness that can be readily converted to film thickness. Whilst the reflected amplitude of the wave is dependent on the frequency component, the measured film thickness is not; this indicates that the quasi-static assumption holds. Measurements of the lubricant film generated in a simple journal bearing have been taken over a range of loads and speeds. The results are compared with predictions from classical hydrodynamic lubrication theory. The technique has also been used to measure oil film thickness during transient loading events. The response time is rapid and film thickness variation due to step changes in load and oil feed pressure can be clearly observed.     

磁化不均匀性对永磁推力轴承性能的影响

通过试验测量了永磁轴承磁环不均匀磁化的分布,分析了磁体间隙对不均匀磁化的影响.运用磁荷理论建立了计算永磁推力轴承承载力模型,研究了磁铁磁化不均性和软磁材料对轴承承载力及刚度的影响.制造了验证该模型的试验装置.计算和试验表明,随着磁隙的减小,磁块间隙的增大,磁力和刚度的变化增大.     

椭圆轴承-转子系统失稳运动数值分析

滑动轴承油膜力是一种强非线性作用力,滑动轴承转子系统是一种典型的非线性动力系统,传统的线性方法无法计算系统失稳后的运动。文中给出用数值积分瞬态模拟对轴承－转子系统非线性振动进行计算分析的方法,并以椭圆滑动轴承－刚性转子系统为例,对系统失稳后的运动状态进行了计算和分析。     

The effect of inlet film boundary conditions on the steady state characteristics of hydrodynamic journal bearings

The well-known solutions for the pressure distribution in the lubricating film of a hydrodynamic journal bearing, satisfying the Reynolds boundary conditions, show a sudden change in the pressure gradient at the position of maximum film thickness, which is possible only if the lubricant is added precisely at this position. Since the pressure develops smoothly because of hydrodynamic action, a correction in the Reynolds boundary conditions is proposed and a new solution for the pressure distribution is obtained. The steady state characteristics of a hydrodynamic journal bearing using the new boundary conditions are compared with the well-known characteristics using the Reynolds boundary conditions.     

轴承结构参数对曲轴主轴承润滑性能的影响

针对曲轴主轴承润滑性能的影响因素研究,建立考虑轴颈直径、轴承宽径比和轴承间隙3种轴承结构参数的曲轴主轴承热弹性流体动力润滑模型,分析不同轴承结构参数下的主轴承最大油膜压力、最小油膜厚度、最高轴承温度和最大摩擦功率损失。计算结果表明：轴承结构参数对主轴承润滑性能有很大影响;当轴颈直径和轴承宽径比变大时,主轴承最大油膜压力会出现减小的情况,最小油膜厚度变大、最高轴承温度升高和摩擦功率损失增加;内燃机主轴承的轴承间隙会随着轴颈直径和轴承宽径比的不同而有不同影响,且轴承间隙对主轴承最高温度和最大摩擦功率损失的影响较为显著。