• KSTLE International Journal
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• v.1 no.2
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• pp.83-90
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• 2000

The surface roughness between a piston ring pack and a cylinder liner directly affects the fuel economy, the oil consumption, and the emission of the engine so that it is very important to clarify the surface roughness effects on the lubrication characteristics. The friction characteristics of the piston ring during engine operations are known to as mixed lubrication experimentally. In this study to simulate the effects of the surface roughness of the piston ring pack on the lubrication characteristics, the mixed lubrication analysis of piston rings was performed using the simplified average Reynolds equation. From the results the surface roughness was found be considerably affects minimum oil film thickness as well as FMEP(Friction Mean Effective Pressure). Especially, the oil ring was the most sensitive on the surface roughness.

• Tribology and Lubricants
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• v.31 no.5
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• pp.205-212
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• 2015

In this research, effects of profile changes of stem section of the plunger on the lubrication characteristics of a fuel injection pump (FIP) were evaluated by hydrodynamic lubrication analysis. The clearance between plunger and barrel was divided into two regions, head and stem. The head was not involved in preventing a decrease of fuel oil pressure. So, research efforts were focused on both edges of the plunger’s stem. The two -dimensional Reynolds equation was used to evaluate lubrication characteristics with variations in viscosity, clearance and profile for a laminar, incompressible, unsteady-state flow. Moreover, the equilibrium equation of moment and forces in the vertical and horizontal directions were used to determine the motion of the plunger. The equations were discretized using the finite difference method. Lubrication characteristics of the FIP were investigated by comparing the dimensionless minimum film thickness, or film parameter, which is the ratio of minimum film thickness to surface roughness. Through numerical analyses, we showed that the profile of the lower edge of the stem had no effect on lubrication characteristics, but the profile of the upper edge had a significant influence on lubrication characteristics. In addition, changes in the profile were more effective in improving lubrication characteristics under low viscosity conditions.

• Tribology and Lubricants
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• v.33 no.4
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• pp.168-186
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• 2017

This paper presents a wear analysis procedure for calculating the wear of journal bearings during the start-up and coast-down cycles of a motoring stripped-down single cylinder engine operating with a tilted shaft. In order to decide whether the lubrication state of a journal bearing is in the mixed-elasto-hydrodynamic lubrication regime, we utilize lift-off speed and MOFT (most oil film thickness) under mixed-elasto-hydrodynamic lubrication regime at the corresponding aligned shaft. We formulate an equation for the modified film thickness in a misaligned journal bearing considering the additional wear volume described in Part I of this study. For this, we use the calculation results of the degree of misalignment and tilting angle obtained after finding the eccentricities of the two bearings supporting the crankshaft of a single cylinder engine. In this Part II, we calculate the wear of journal bearings using the fractional film defect coefficient, the asperity load sharing factor, and the modified specific wear rate for the application of mixed-elasto-hydrodynamic lubrication regime. We show that the accumulated wear volume after turning the ignition switch on and off once, increases to ${\sigma}=39{\mu}m$ and then decreases from ${\sigma}=39{\mu}m$ with increasing in surface roughness.

• Tribology and Lubricants
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• v.21 no.1
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• pp.8-15
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• 2005

In this study a general Galerkin FE lubrication analysis method is utilized to analyze the complex lubrication performance of a spiral groove seal, which is being designed and developed for a high-speed flying object application operating at a high-speed of over 50,000 rpm. As at the equilibrium seal clearance the axial stiffness of the seal is predicted to have almost such a constant high value of $1.04\times10^8\;N/m$ regardless of a rotating speed, the seal is expected to maintain a stable thickness of lubrication film under a certain external excitation acting. Also, as even at an ultra high-speed of 80,000 rpm the axial damping of the seal is shown to have a rotatively high value of 5,775 N-s/m, the dynamic stability of the seal system at the axial degree of freedom is assured well enough.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.101-102
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• 2007

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.405-406
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• 2002

The main subject of this paper is analyzing the patterns of maximum oil film pressure and the minimum oil film thickness under various pre-conditions of geometric shape as functions of bearing groove and proceeding oil hole in the connecting rod bearing. As the major analytical tool, elastohydrodynamic lubrication analysis has been applied and two-intertwined results of maximum oil film pressure and minimum oil film thickness have been compared and analyzed using EXCITE program. From computed results, the optimal lubrication conditions as geometric shape of bearing groove and the proceeding oil hole have been investigated. This may be useful for the bearing designer as a firm reference.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.200-206
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• 2002

Pressure and film thickness of contacting surfaces between teeth of the involute spur gear in lubricated condition were studied by a numerical method. Dynamics of the gear and pinion was considered to gel ail accurate initial clearance between gear teeth. The 3-dimensional non-steady elastohydrodanamic lubrication analysis on the gear teeth showed a slight higher pressure at the inlet region of the contacting face as well as pressure spike at the outlet region and a more thick film thickness than that of steady condition.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.685-692
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• 2001

This paper reports on the mixed lubrication characteristics between the cam and the tappet contact surface of direct acting type valve train systems. First, the dynamic characteristics are solved by using the lumped mass method to determine the load conditions at the contact point. Then, the minimum oil film thickness is calculated with consideration of elastohydrodynamic line contact theory and the friction force is obtained by using the mixed lubrication model which separates the hydrodynamic and the boundary friction. Finally, the average surface temperatures are calculated by using the flash temperature theory. The results show that, there are some peaks in the friction force due to the asperity contact friction, and flash temperature at the position of minimum oil film thickness. It is thought that there is a relationship between the surface temperature and cam surface wear, and therefore, the analysis on the worn cam profile has been performed.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.147-154
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• 2000

A numerical procedure to analyze 3-dimensional elastohydrodynamic lubrication was applied on the cam-roller contact of the valve mechanism for a 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. An effective profiling method for the roller edge was suggested using the results of elastohydrodynamic lubrication analysis and the peak pressure was removed completely with the new profiling.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.430-435
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• 2008

This research deals with the implementation hydrodynamic (HD) lubrication system with an integration of multibodydynamics (MBD) in order to analyze bearing lubrication characteristics such as pressure distribution and oil film thickness dynamically. The HD solver developed newly will transmit force and torque data to MBD solver, and receive position and velocity data from it continuously. After an analysis, we will verify the result with existing commercial software. Moreover, other functions like adjusting size of mesh grid, setting oil hole & groove effects, and consideration of thrust force will be introduced.