• 제목/요약/키워드: 열 유체 윤활

검색결과 46건 처리시간 0.019초

변화하는 밀도와 비열을 고려한 고속 저어널 베어링의 열유체 윤활해석 (Thermohydrodynamic Lubrication Analysis of High Speed Journal Bearing Considering Variable Density and Specific Heat)

  • 전상명;장시열
    • Tribology and Lubricants
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    • 제17권4호
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    • pp.297-306
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    • 2001
  • Under the condition of variable density and specific heat, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined within some degree of Journal misalignment. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the condition of variable density and specific heat play important roles in determining friction and load of Journal bearing at high speed operation.

다양한 열전달 경계조건을 고려한 고속 저어널 베어링의 난류 열유체 윤활 연구 (A Study on Thermohydrodynamic Turbulent Lubrication of High Speed Journal Bearing Considering Various Thermal Conditions on Walls)

  • 전상명;장시열
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2000년도 제31회 춘계학술대회
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    • pp.93-98
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    • 2000
  • Turbulence on the journal bearing operation is examined. And the thermal variability is studied for isothermal, convective and adiabatic conditions on the walls within some degree of journal misalignment. An efficient algorithm for the solution of the coupled turbulent Reynolds and energy equations is used to examine the effects of the various factors. The calculation data of turbulent analysis are compared with the ones of laminar analysis. Heat convection is found to play but a small role in determining friction and load. The friction distribution patterns through inside a journal bearing now appear different with high values at the front part of the bearing due to the high speed and low temperature, and a sudden decrease past the pressure maximum.

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멀티그레이드 윤활유의 탄성유체윤활 유막 측정 연구 (A study on the EHL film behavior measurement for the multigrade lubricant)

  • 장시열;김승재;김재홍;배대윤;유성춘
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2004년도 학술대회지
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    • pp.269-274
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    • 2004
  • It is important to decide the minimum film thickness and viscosity variations of a multigrade lubricant in the contact surface under the high pressure conditions. By carrying out acceleration, deceleration, and various sliding-rolling ratio movement between two contact bodies, it is experimented that film formation variations in the contact surface are captured with multigrade lubricants in order to exactly investigate the variations of film formations. Optical interference images are continuously captured with high resolution CCD camera during the captured period of acceleration, deceleration. The friction forces between the contacting bodies are also measured simultaneously with the film formation.

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탄성변형을 고려한 엔진베어링의 동적 거동에 대한 연구 (A Study on the Dynamic Behaviors of Engine Bearing with the Consideration of Elastic Deformation in the Con-Rod System)

  • 장시열;박계민
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2004년도 학술대회지
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    • pp.275-282
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    • 2004
  • The engine bearing transmits the powers from cylinder to crankshaft with small clearance between con-rod and crankpin. The minimum oil film thickness is a significant parameter in the operation of bearing. The contact pressure of bearing should be considered for the reason that elastic deformation of bearing be caused by contact pressure of bearing. There are important factors which are maintaining of minimum oil film thickness expecting of the length of maximum and minimum oil film thickness with changing of the loads to keep running normally. Furthermore, this study is very crucial to develop the design of engine bearing and crankshaft system.

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축방향 프로파일 형태에 따른 롤러의 탄성유체윤활 연구 (A Study on the Elastohydrodynamic Lubrication of Roller Contact according to Axial Profiles)

  • 장시열;김완두;김민철
    • Tribology and Lubricants
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    • 제23권5호
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    • pp.187-194
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    • 2007
  • The profile of the roller in the axial direction is the main design factor in order to increase endurance life against the contact fatigue due to the stress concentration along the edge of the roller. Even under the elas-tohydrodynamic lubrication (ehl) conditions, the stress concentration along the edge of the roller greatly worsens the fatigue life both for the roller and contacting body. In this study, roller contacts of finite axial length are studied for the film thickness and pressure of ehl. For the real contact behaviors under the ehl conditions, multigrid and multi-level method is applied so that much higher loading conditions can be investigated. Several axial profiles of roller are investigated to verify how both ehl film and pressure are generated and some of them are recommended for the ehl contact condition.

Herschel-Bulkley 모델을 이용한 그리스 열탄성유체윤활 문제의 수치해석 (A numerical analysis of grease thermal elastohydrodynamic lubrication problem using Herschel-Bulkley model)

  • 유진규;김경웅
    • Tribology and Lubricants
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    • 제11권3호
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    • pp.31-39
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    • 1995
  • Grease thermal elastohydrodynamic lubrication (TEHL) problems of line contacts are analyzed numerically. The effects of temperature and rheological paraineters on grease TEHL are investigated using the Herschel-Bulkley model as a theological model of greases. The pressure distribution, the shape of grease film, mean film temperature and surface temperature of solid wall in line contacts are obtained. It is found that thermal effects on the minimum film thickness become remarkable at high rolling speeds. The effect of yield stress of Herschel-Bulkley model on minimum film thickness is negligible, while the theological index and viscosity parameter have significant effects on minimum film thickness.

능동 제어 되는 외부가압 공기 저어널 베어링의 안정특성에 관한 연구 (A Study on the Stability Characteristics of Actively Controlled Externally Pressurized Air Journal Vearing)

  • 이정배;김경웅
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1996년도 제24회 춘계학술대회
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    • pp.99-105
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    • 1996
  • 공기 베어링은 마찰과 열 발생이 적고 회전 정밀도가 우수하여 고속 회전하는 축을 지지하는 용도로 많이 사용되고 있다. 그러나 공기 베어링도 유체 베어링이라면 어느것이나 갖는 Whirl 불안정성이라는 치명적인 결점을 갖는데 현재 이것의 발생 시점이 공기 베어링을 사용하는 시스켐에 있어서 고속화의 한계로 되어있다. 본 논문에서는 불안정성의 원인이 되는 동압 발생을 억제할 수 있는 방법으로 베어링의 위치가 축의 위치에 대해 일정한 각도 지연을 갖도록 제어되는 것을 제안하고 여러 각도지연 크기와 제어게인에 따른 안정특성을 이론 해석을 통해 조사하였다.

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탄성 유체 윤활에서의 유막 두께 측정에 관한 정성적 분석 (Qualitative Analysis of Film Thickness in Elastohydrodynamic Lubrication)

  • 최언진;장시열
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1999년도 제29회 춘계학술대회
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    • pp.147-155
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    • 1999
  • The film thickness and shape of elastohydrodynamic lubrication is measured by optical interferometer, which is the most precise method for EHL film measurement. However the interpretation of the image pattern from optical viscometer is not easy for two-dimensional shape. A newly developed method of image processing makes it possible to evaluate the film thickness and shape in every point of contact region with two dimensional aspects. In this study, we captured film shape of EHL film from the monochromatic incident light with the Image processing method, which uses phase shift method, and obtained the image analysis method for gray level image in order to qualitatively evaluate film shapes.

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열유체 윤활해석에 의한 표면 거칠기가 마찰거동에 미치는 영향 고찰 (The Influence of Surface Roughness on Thermohydrodynamic Analysis)

  • 김준현;김성걸;김주현
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집C
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    • pp.299-304
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    • 2001
  • An approach is developed for parametric investigation of the influence of the surface roughness on thermohydrodynamic analysis with film conditions which systemically occur in journal bearings. A parametric investigation is performed for predicting the bearing behaviors such as pressure and temperature distributions in lubricating films between the stationary and moving surfaces determined by absorbed layers and interfaces on the statistical method for rough surface with Gaussian distribution. The layers expressing the effects of surface roughness are expressed as functions of the standard deviations (${\sigma}$) of each surface and surface orientation (j) to explain the flow patterns between both rough surfaces. The coupled effect of surface roughness and shear zone dependency on hydrodynamic pressure and temperature has been found by solving the present model in non-contact mode and contact mode, respectively.

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탄성유체윤활 영역에서 점도지수 향상제의 첨가량에 따른 마찰력 측정연구 (Friction Force Measurement of Elastohydrodynamic Lubrication with Viscosity Index Improvers)

  • 공현상;장시열;박경근
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2002년도 제35회 춘계학술대회
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    • pp.267-271
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    • 2002
  • Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the characteristics of a certain lubricant, it is also important to get the information of traction force as well. In this work, we developed the device for measuring friction force of ehl contact condition together with the film thickness. To verify the validity of the measuring system, the friction force and film thickness under ehl condition are measured with the variation of additive ratios of viscosity index Improvers.

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