• Tribology and Lubricants
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• 제16권3호
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• pp.201-207
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• 2000

The numerical procedure to analyze a non-steady 3-dimensional elastohydrodynamic lubrication on the cyclically loaded contact has been newly developed. The procedure was applied on the cam-roller contact of the valve mechanism for the marine diesel engine. Both the pressure distribution and the film thickness between the cam and roller follower were calculated for each time step of the whole cycle. The pressure spike is shown at the outlet of the roller edge and it is getting higher as the external load is increased. The film thicknesses in the result of the non-steady analysis have a tendency to increase compared to those in the result of the analysis with the assumption of steady state. Therefore, the surface roughness of the non-steady contact need not be limited below that of the steady contact of the equivalent operating conditions.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 추계학술대회
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• pp.176-182
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• 1996

This paper describes an empherical equation which is to predict the engine condition of the supersonic aircraft. The equation, which is a function of running time of engine and engine oil, is derived from the trend analysis of JOAP data. Qualitative analysis is carried out to make up for the weak points in the current JOAP system. Also wear debris collected from the abnormal engine is analyzed by EDS to detect the damaged parts of engine.

• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.928-934
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• 2000

This paper describes a method developed for the simulation of ring pack lubrication characteristic in an internal combustion engine. In general, the quantity of oil supply for piston ring lubrication may be insufficient in filling the entire volume formed at the interference between the piston ring and the cylinder liner. Thus the oil starvation condition should be considered in analyzing piston ring lubrication. In order to reasonably estimate the amount of oil left over on the cylinder liner, the flow rate at the posterior portion of the interface should be calculated with an adequate boundary condition that confirms flow continuity condition. In this analysis, oil starvation and open-end boundary conditions are considered at the inlet and outlet of the piston rings. The lubrication characteristic of each piston ring is obtained by an iterative method with sequential steps. It is revealed that piston rings are operated under oil starvation in most operating cycles and the result under these conditions are quite different from that with the fully-flooded assumption.

• Tribology and Lubricants
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• 제13권2호
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• pp.46-51
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• 1997

Crosshead bearings in two-stroke marine diesel engines are operated under severe conditions of lubrication because the load on the bearing is unidirectional and the sliding speed is very low and oscillatory. In this paper, the motion of journal in a bearing is investigated using the lubrication theory. Several locus paths are presented to show the effects of oil groove size, bearing clearance and oil inlet pressure. It is found that the minimum film thickness is affected by the oil groove and bearing clearance, and the oil groove is an important design factor.

• Tribology and Lubricants
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• 제27권4호
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• pp.183-192
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• 2011

In this study, using the governing equations for thermohydrodyamic lubrication involving the homogeneous mixture of incompressible fluid derived by based on the principle of continuum mechanics, it is discussed the effects of water dispersed within engine oil on the performance of high speed journal bearing of a turbocharger. The governing equations are the general equations being able to be applied on the mixture of Newtonian fluid and non-Newtonian fluid. Here, the fluid viscosity index, n of power-law non-Newtonian fluid is supposed to be 1 for the application of the journal bearing on a turbocharger lubricated with the mixture of two Newtonian fluids, water dispersed within engine oil. The results related with the bearing performance are showed that the friction force and bearing load capacity decrease as increasing the volume percent of water.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.19-24
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• 1997

The operating torque and tribological characteristics of the cam/tappet system in an I.C. engine have an important effect on engine efficiency. In this paper, we measured the torque of cam/tappet system with respect to the oil temperature and camshaft speed to characterize the tribological behavior. Also, accelerated test was performed to analyze the wear characteristics of cam/tappet interface. The torque of the cam/tappet system decreased with respect to camshaft speed and was not significantly affected by the oil temperature. The results of accelerated test showed that the running-in wear occurred during the tests and the center of the tappet was mainly damaged by the rolling and sliding friction.

• 대한기계학회논문집
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• 제18권6호
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• pp.1510-1519
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• 1994

It is important to understand the friction characteristics between piston-ring assembly and cylinder wall for the friction loss reduction as well as the solution of problem such as scuffing wear and oil consumption. A new system was developed for the piston-ring assembly friction force measurement. This system was applied to the friction force measurement to find its functional relationship with variables such as engine speed, oil viscosity, and engine load. The friction mean effective pressure(fmep) was found to have a linear relationship with$(\vpsilon{U})^{0.42}$ under motering and with$(\vpsilon{U})^{0.45}$ under firing operations, where $\vpsilon$ is the kinematic oil viscosity and U is mean piston speed.

• Tribology and Lubricants
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• 제28권2호
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• pp.81-92
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• 2012

To product multi-grade oil like engine oil, a sort of mineral base oil is mixed with a fundamental additive liquid package and a polymer liquid as viscosity index improver in order to improve the lubricating property of oil. That is, engine oil is the mixture of more than two fluids. In this paper, it will be systematically organized the governing equation describing non-Newtonian thermo-hydrodynamic lubrication related with the mixture of incompressible fluids based on the principle of continuum mechanics. Then, in order to find how the thermal analysis effect on the bearing performance lubricated with the mixture of multi-fluids, it will be compared to the performances between the mixture of each liquid to be blended and multi-grade engine oil as a single fluid in a high speed journal bearing. It is found that, in the case of lower viscosity oil, the difference of pressure distribution between the above two cases turns out to be existed, even if the load capacity is same level.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.244-251
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• 1998

This paper presents case studies on the oil related failures in automotive engines. In this study, engine oils play an important roles as a friction reducing matehals and should be supplied to a tribological machine elements sufficiently. The starvation or depletion of a lubricant may seriously produce the tribological failures on the rubbing parts of the engine.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.143-148
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• 2001

ILSAC GF 3/API SL specification will be adopted in July 2001. The background and characteristics of GF3 specification is reviewed. GF3 specification consists of five new engine tests, two new bench tests and new limits on three bench tests currently used to define ILSAC GF-2. GF 3 engine oil shows good performance compared to GF2 engine oil in fuel efficiency, protecting ability the emission catalyst and high temperature oxidation stability.