• Title/Summary/Keyword: Fluid film journal bearing

Search Result 113, Processing Time 0.026 seconds

Study on Boundary Lubrication in the Sliding Bearing System under High Load and Speed (고하중과 고속 미끄럼 베어링 시스템의 경계윤활에 대한 연구)

  • 장시열
    • Tribology and Lubricants
    • /
    • v.15 no.3
    • /
    • pp.248-256
    • /
    • 1999
  • Many tribological components in automobile engine undergo high load and sliding speed with thin film thickness. The lubrication characteristics of the components are regarded as ether hydrodynamic lubrication or boundary lubrication, whereas in a working cycle they actually have both characteristics. Many modem engine lubricants have various additives for better performance which make boundary film formation even under hydrodynamic lubrication regime. Conventional Reynolds equation with the viewpoints of continuum mechanics concerns only bulk viscosity of lubricant, which means that its simulation does not give insights on boundary lubrication characteristics. However, many additives of modern engine lubricant provide mixed modes of boundary lubrication characteristics and hydrodynamic lubrication. Especially, high molecular weight polymeric viscosity index improvers form boundary film on the solid surface and cause non-Newtonian fluid effect of shear thinning. This study has performed the investigation about journal bearing system with the mixed concepts of boundary lubrication and hydrodynamic lubrication which happen concurrently in many engine components under the condition of viscosity index improver added.

A Study on the Change in the Film Thickness of Ball Bearing in Starved EHL (윤활유 부족 상태에서의 볼 베어링 유막 두께 변화에 대한 연구)

  • Jung, SoonBi;Lee, Bora;Yu, YongHun;Cho, YongJoo
    • Tribology and Lubricants
    • /
    • v.33 no.3
    • /
    • pp.119-125
    • /
    • 2017
  • In this study, we perform a numerical analysis to predict the film thickness and lubrication regions for a thrust ball bearing under different operating conditions. Film thinning and replenishment affect the film thickness in starved lubrication. As the inlet meniscus position is brought to the edge of the Hertz contact, the thin film thickness is calculated as starved equation. We use a film replenishment model to determine the recovery film thickness between rolling elements. We use a hydrodynamic model to describe film recovery, that results from the effects of surface tension. In this model, we consider the surface tension gradient in fluid depression as the driving force for fluid recovery. We use Fourier transform method to determine the time-dependent depth of depressed oil. We calculate the change in the central film thickness graphically by using the recovery equation in starved elastohydrodynamic lubrication(EHL) under operating conditions that include numbers of balls, sliding velocity, applied force, and ambient film thickness. We evaluate the degree of starvation by using the distance from the center of the contact area to the meniscus position. Parched lubrication, a phenomenon where the film thickness decreases consistently, occurs at the severe condition. We determine optimal values with respect to the numbers of balls, and sliding velocity. The investigation can contribute to the design operating conditions for proper lubrication.

Thermohydrodynamic Analysis Considering Flow Field Patterns Between Roughness Surfaces (미세 표면 거칠기에 지배되는 박막 유동장 형태를 고려한 윤활거동)

  • 김준현;김주현
    • Tribology and Lubricants
    • /
    • v.19 no.3
    • /
    • pp.167-177
    • /
    • 2003
  • The study deals with the development of a thermohydrodynamic (THD) computational procedure for evaluating the pressure, temperature and velocity distributions in fluid films with very rough geometry. A parametric investigation is performed to predict the bearing behaviors in the lubricating film having the absorbed layers and their interfaces determined by the rough surfaces with Gaussian distribution. The layers are expressed as functions of the standard deviations of each surface to characterize flow patterns between both the rough sur-faces. The velocity variations and the heat generation are assumed to occur in the central (shear) zone with the same bearing length and width. The coupled effect of surface roughness and shear zone dependency on hydrodynamic pressure and temperature has been found in non-contact mode. The procedure confirms the numerically determined relationship between the pressure and film gap on condition that its roughness magnitude is smaller than the fluid film thickness.

A study on the heat generation into air film as rotating of high speed journal in the air journal bearing (공기저어널 베어링에서 저어널의 고속회전시 공기유막내의 열발생에 관한 연구)

  • 이종열;성승학;이득우;박보선;김태영
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
    • /
    • 2002.04a
    • /
    • pp.82-86
    • /
    • 2002
  • The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite difference method analysis obtain temperature rise and temperature distribution of housing. For the analysis, air fluid film model is built and temperature rise and distribution in thermal steady state are computed for each rotational speed. Generally, it is said that the heat generation of air bearing is negligible. But the heat generation in air film by heat dissipation can not be negligible especially into high-speed region of the journal. In case that the heat generation of air spindle system is high, natural frequency of the spindle system becomes lower when the thermal state is in steady-state and it means the changes of air bearing stiffness due to the change of bearing clearance. It is shown that the temperature rise of air spindle system causes thermal expansion and induces the variation of bearing clearance. In consequence the stiffness of air bearing becomes smaller.

  • PDF

An Analysis of Characteristics of Air-Lubricated Foil Journal Bearings (공기윤활 포일 베어링의 특성해석)

  • 김종수;이준형;최상규
    • Tribology and Lubricants
    • /
    • v.17 no.2
    • /
    • pp.97-108
    • /
    • 2001
  • This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.

A Finite Element Formulation for Vibration Analysis of Rotor Bearing System

  • Park, Myung-Jin
    • The Journal of the Acoustical Society of Korea
    • /
    • v.15 no.4E
    • /
    • pp.37-44
    • /
    • 1996
  • To get accurate vibration analysis of rotor-bearing systems, finite element models of high speed rotating shaft, unbalance disk, and fluid film journal bearing are developed. The study includes the effects of rotary inertia, gyroscopic moment, damping, shear deformation, and axial torque in the same model. It does not include the axial force effect, but the extension is straighforward. The finite elements developed can be used in the analysis design of any type of multiple rotor bearing system. To show the accuracy of the models, numerical examples are demonstrated.

  • PDF

An Experimental Study on Ram Pressure and THD Performance of Pivoted Pad Thrust Bearing (피봇식 주력베어링의 선단압력과 THD성능에 관한 실험적 연구)

  • 박홍규;김경웅
    • Tribology and Lubricants
    • /
    • v.2 no.1
    • /
    • pp.61-68
    • /
    • 1986
  • Effects of the ram-pressure on the THD-performance of pivoted pad thrust bearings are investigated experimentally. A sector-shaped tilting pad thrust bearing and a rotating disk are used. Temperature distribution on the disk surface as well as on the pad surface, distribution of the pressure generated within the fluid film, and the film thickness are measured continuously in the circumferential direction after thermal equilibrium is established. The ram-pressure is proportional to the mean pressure of oil film and to the rotational speed of the disk and affects the maximum pressure and the pressure distribution. The temperature rise on the mating surface of the disc and the pad, contacting with the oil film, is proportional to to the bearing load and the disk speed. The ram-pressure and the temperature rise on the disk surface are dominant factors that affect the THD-performance of pivoted pad thrust bearings.

Characteristics of Friction Torques and Lubrication in High Speed Angular Contact Ball Bearings (고속 앵귤러 콘택트 볼베어링의 마찰 토크 및 윤활 특성)

  • 반종억;김경웅
    • Tribology and Lubricants
    • /
    • v.13 no.4
    • /
    • pp.47-52
    • /
    • 1997
  • Friction torques, electrical contact resistances and bearing temperatures were measured on high speed angular contact ball beatings for the spindle of machine tools. The test bearings ran with oil-air lubrication at the thrust loads from 320 N to 1920 N and at the rotational speed of up to 12000 rpm. Electrical contact resistances between balls and races were measured to evaluate the formation of the lubricant film in the contact area. The test results with sufficient lubrication showed that the variations of friction torques were sensitive to the thrust loads and the rotational speeds, and that the friction torques were higher than those with insufficient lubrication. With insufficient lubrication and high thrust loads, the collapse of the lubricant film was detected even at a high rotational speed. It was concluded that these high speed beatings to run in condition of fluid lubrication should require monitoring not only the temperature increase of the bearing but also the lubricant film formation in contact areas resulting from the change in the applied load and the lubricant amount.

Surface Lay Effects on the Lubrication Characteristics in the Valve Part of a Swash-plate Type Axial Piston Pump (표면가공무늬가 사판식 액셜 피스톤펌프의 밸브부 윤활특성에 미치는 영향에 관한 연구)

  • Shin, Jung-Hun;Kang, Bo-Sik;Kim, Kyung-Woong
    • Tribology and Lubricants
    • /
    • v.28 no.1
    • /
    • pp.12-18
    • /
    • 2012
  • This application study of a swash-plate type axial piston pump was concerned about the lubrication characteristics between cylinder barrel and valve plate which are the main rotating body and its opposite sliding part respectively. A computer simulation was implemented to assess bearing and sealing functions of the fluid film between cylinder barrel and valve plate. A numerical algorithm was developed to facilitate simultaneous calculations of dynamic cylinder pressure, 3 degree-of-freedom barrel motions considering inertia effect, and fluid film pressure assuming full fluid film lubrication regime. Central clearance, tilt angle, and azimuth angle of the rotating body were calculated for each time step. Surface waviness was found to be an influential factor due to the small fluid film thickness which can appear in flat land bearings. Five surface lays which can form on the lubrication surface in accordance with machining process were defined and analyzed using the simulation tool. Oil leakage flow and frictional torque in the fluid film between cylinder barrel and valve plate were also calculated to discuss in the viewpoint of energy loss. The simulation results showed that in actual sliding conditions proper surface non-flatness can make a positive effect on the energy efficiency and reliability of the thrust bearing.

Thermal Deformation Induced Preload Changein the Tilting Pad Journal Bearing (열변형으로 인한 틸팅패드 저널베어링의 예압 변화)

  • Suh, Junho;Hwang, Cheolho
    • Tribology and Lubricants
    • /
    • v.32 no.1
    • /
    • pp.1-8
    • /
    • 2016
  • This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.