• Tribology and Lubricants
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• 제33권1호
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• pp.23-30
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• 2017

The electric controlled marine diesel engine has fuel pump generating the high pressurized fuel for fuel injection to combustion chamber via a common rail. Fuel pump consists of a cam-roller system. Journal bearing installed between a roller and a cam-roller pin is subjected to fluctuating heavy and instant loads by cam lift. First, Kinematic analysis is carried out to predict bearing loads during one cycle acting on the journal bearing. Second, flexible multi-body dynamic analysis and transient elasto-hydrodynamic(EHD) lubrication analysis for journal bearing considering elastic deformation of cam-roller pin, roller and bearing are conducted using AVL EXCITE/PU software to predict lubrication performance. The clearance ratio and journal groove shape providing lubrication oil are important parameter in bearing design having good performance and can be changed easier than other design parameters such as diameter, width, oil supply pressure and bearing material grade. Generally, journal bearing performance is represented by the minimum oil film thickness(MOFT) and peak oil film pressure(POFP). As well as the traditional design parameters(MOFT, POFP), in this study, temperature rise of lubrication oil is also evaluated through the side leakage flow of supplied oil. By the evaluating MOFT, POFP and temperature rise, the optimum bearing clearance ratio is decided.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.113-114
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• 2002

Radial, tilting 12-pad proceeding bearings are applied as the radial bearings of vertical rotors of water turbines. The mean loads are stable at the peripheral speeds of proceeding reaching 50 m/s. The operation of tilting 12-pads proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions have been obtained by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss, oil flow, maximum oil film pressure, maximum temperature have been computed for different load angle of bearing.

• Journal of Mechanical Science and Technology
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• 제15권6호
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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.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.95-96
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• 2002

The operation of proceeding bearing in the conditions of misaligned axis of proceeding and bush leads to the load concentration on the bearing edges causing further mixed lubrication conditions, unstable operation and intensive wear of mating parts. For the design process of proceeding bearing the knowledge of static characteristics determined from the oil film pressure and temperature distribution is very important. For the 3-lobe proceeding bearing, the pressure, temperature and viscosity fields, load capacity, minimum oil film thickness, power loss, oil flow and maximum oil film temperature have been determined by iterative solution of the Reynolds', energy and viscosity equations. The paper introduces the results of theoretical investigations of static characteristics of 3-lobe proceeding bearing operating at misaligned axis of proceeding and bush. An effect of misalignment ratio, length to diameter ratio of the proceeding bearing, the lobe clearance ratio on the static characteristics was investigated. Laminar, adiabatic model of oil film for the solution of Reynolds, energy and viscosity equations was applied.

• Tribology and Lubricants
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• 제20권3호
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• pp.119-124
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• 2004

Engine bearing system is generally affected by aeration. In this paper, the aeration effects on the engine crankshaft bearing system were studied. To do this, unsteady oil flow analysis on the engine crankshaft oil circuit system was carried out. And aeration effects on the bearing system were simulated to figure out lubrication characteristics of the each bearing such as oil flow rate, minimum oil film thickness, friction loss and increase of oil temperature.

• KSTLE International Journal
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• 제1권2호
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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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• 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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• 제31권5호
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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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• 제8권2호
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• pp.50-63
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• 1992

The minimum oil film thicknesses (MOFT) in the crankshaft main bearings of a 1.5 liter, L-4, gasoline engine are measured and calculated to study the dynamically loaded engine bearing. The MOFT are measured simultaneously at each of the five main bearings using the total capacitance method(TCM). To improve the reliability of the TCM, a reasonable determination method of bearing clearance is introduced and the effects of bearipg cavitation and aeration on the test results are analyzed. Also the crankshaft is grounded by means of a slip ring instead of the friction contact method to improve the test precision. The calculation is based on the model of statically determinate beam, short bearing approximation and Mobility method. From the comparison between the measured and calculated MOFT curves, it is found that a qualitative similarity exists between them, but in all cases, measured MOFT are smaller than that of calculated. The crankshaft vibration and the imbalance of the load distribution between the engine bearings have important influence upon the MOFT curve. So it is found that the calculation result from the model of the statically determinate beam has a limitation in predicting bearing performance.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.468-475
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• 2002

This paper reports on the friction characteristics of a piston ring pack with consideration of mixed lubrication. The analytical model is presented by using the average flow antral asperity contact model. The effect of operating condition, and design parameters on the MOFT, maximum friction force, and mean frictional power loss are investigated. Piston ring prick shows mixed and hydrodynamic lubrication characteristics. From the predicted results, it was fand that the ring tension and height of surface roughness have great influence on the frictional power losses in a ring pack. Especially, ring tension is a dominant factor for the reduction of friction loss and maintenance of oil film thickness.