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This paper discusses the effects of lubricant viscosity on the friction characteristics of engine bearing and cam/tappet which are the typical moving parts of an engine and operate in different lubrication regimes. Based on the measured crankshaft temperatures, we calculated the friction coefficient of the engine bearing according to Sommerfeld number by a simple heat equilibrium equation. The oil film thicknesses between cam and tappet were measured in a motored cylinder head which had a direct acting type overhead camshaft. The boundary and viscous friction components were estimated separately according to a parameter defined as the ratio of the central oil film thickness to the composite surface roughness. These two friction components were added to calculate the friction coefficient. Finally, the motoring friction torque was measured and compared with the estimated friction coefficient.

In order to understand and resolve the exhaust valve carbon sticking problem, the engine parameters effective on the phenomenon are shown by bench tests. Based on the results, a new test code which can evaluate the exhaust valve sticking has been developed. And by using the test code, the effects of engine hardware, gasoline properties, and warm-up enrichment are shown. Finally, the detailed mechanism of the exhaust valve carbon sticking is clarified and solution to it is proposed.

In order to understand the relationship between the location of piston ring gap and instantaneous change of oil consumption during engine operation, the ring rotation and instantaneous oil consumption were measured simultaneously in a hydrogen fueled single cylinder spark ignition engine. A radioactive-tracer technique was used to measure the rotational movement of piston ring. Two kinds of isotopes(60Co and 192Ir) with different energy level were mounted to the top and 2nd rings to measure each ring's movement independently. The instantaneous oil consumption was obtained by analyzing CO2 concentration in exhaust gas. From the result of ring rotational movement, typical patterns of ring rotation were obtained as follows; Rotational movements are usually initiated by changing the operating conditions. Piston rings tend to rotate easily under low load condition. The rotation speed of ring usually ranged in 0.2∼0.4 rev/min for top ring and 0.5∼0.6 rev/min for 2nd ring.

In order to study the effect of the oil aeration rate on bearing reliability, the minimum oil film thicknesses(MOFT) were measured by the change of oil aeration rate using the total capacitance method(TCM), and at the same time, to study the appropriateness as an index of bearing reliability, crankshaft temperatures were measured. The minimum oil film thicknesses were measured at each of five main bearings and No.1 connecting rod bearing. A scissor type linkage system was employed to measure the minimum oil film thickness of connecting rod bearing. Special techniques were devised to inject air into the oil, and to monitor the aeration rate by an on-line measurement system. The measured aeration rates are proportional to the oil pressure drop. The change of the MOFTs are very slight up to a 30% aeration rate in the test engine. But if the oil aeration rate exceeded 30%, the minimum oil film thicknesses were changed.

Heat balance and metal temperatures of 1.5 ℓ and 2.0 ℓ DOHC(Double Over-head Camshaft) engines were measured and compared before and after break-in. The cylinder head break-in and cylinder block break-in were done individually in order to observe the each effect of break-in of them. After the engine break-in, the heat rejection to coolant was decreased and the heat loss through the exhaust gas was increased, but the heat rejection to oil did not show a significant change. The engine metal temperatures were also dropped after break-in. In this paper, those changes after the engine break-in were analyzed with two factors such as the cylinder head and the cylinder block, and it was proved that the changes were resulted from the thermal insulation effect of carbon deposits in the exhaust port and the reduction of friction loss. We suggested a scheme to reduce the size of vehicle cooling system by quantitatively analyzing the effect of the engine break-in.

This paper describes the development of THC reduction technologies compliant with SULEV regulations. Technologies embodied by the developmental work include improvement of fuel spay atomization, quick warm-up through coolant control shut off, and acceleration of fuel atomization for the fast rise of cylinder head temp inside the water jacket as well as the improvement of combustion state. The technologies likewise entail reduced HC while operating in lean A/F condition during engine warm-up with the cold lean-burn technology, individual cylinder A/F control for improvement of catalytic converting efficiency, aftertreatment such as thin-wall catalyst, HC absorber and EHC and etc., through vehicle application evaluation in cold start. We carried out an experimental as well as a practical study against SULEV regulations, and the feasibility of adopting these items in vehicle was likewise investigated.

The minimum oil film thicknesses(MOFT) in the connecting-rod bearings of a 1.5 liter, L-4, gasoline engine are measured up to 5500 rpm and calculated to study the dynamically loaded engine bearings. Short bearing approximation and Mobility methods are used for theoretical analysis of oil film characteristics. Also cylinder pressure, crank-pin surface temperature and bearing temperature are measured and used as the input data of theoretical analysis. The MOFT are measured by the total capacitance method(TCM). To improve the reliability of the test results, a reasonable determination method of bearing clearance is introduced and used, and the effects of cavitation and aeration on the test results are neglected. Also the crankshaft is grounded by means of a slip ring. A scissor type linkage system was developed to measure the MOFT and bearing temperature.

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 bearing 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.

In order to investigate the characteristics of top ring groove deposit formation in gasoline and diesel engine, engine test and simulation test were performed. From component analysis of used oils sampled from actual running engines, oxidation and nitration for gasoline engine and soot content for diesel engine were selected as main parameters for evaluating oil degradation. In gasoline engine, deposit formation increases linearly with oxidation and nitration, and especially, oil oxidation is a dominant factor on the deposit formation rather than nitration. And, deposit formation increases gradually in low temperature ranges below 260°C even if oils are highly oxidized, but it increases rapidly if piston top ring groove temperature is above 260°C. In diesel engine, deposit formation is highly related to soot content in lubricating oils.

The in-cylinder three-dimensional unsteady analysis on the fluid patterns were scrutinized using computational fluid dynamics code. The 3D CAD data were created using the 3D CAD modeling software and the computational meshes were generated considering the movements of intake valves and piston. The calculated results of in-cylinder flow patterns for the pent-roof type combustion chamber were in good agreements with the unsteady water rig experimental results. To investigate the influences of the intake port inclined angle variations on the in-cylinder flow patterns and the resulting in-cylinder tumble ratio, each type of intake port were simulated with the intake port inclined angle variations. The results show that as the intake port inclined angles become smaller, the in-cylinder tumble ratio were strengthened. If the intake port inclined angle was larger than 30 degree, the in-cylinder tumble ratio was saturated.

In this study, the mass of THC is reduced almost 40 percent with spark timing ATDC 7.8CA during 15 seconds from engine start in phase 1 LA4 mode, comparison with TDC 2.8CA (Figure 1, Table 3). One of the reason of HC reduction in vehicle test is reduction of raw THC concentration before CCC (Closed Coupled Catalyst) which is 36% lower level (Figure 3, Table 3). The other reason is that the LOT (Light Off Time) of catalyst is shortened from 34 seconds to below 20 seconds (Figure 7, Table 3). As the spark timing is retarded with same intake air quantity and same RPM, BMEP is reduced (Equation (3), Figure 9). Therefore in order to operate in an idle RPM in vehicle, the mass of intake air should be increased (Figure 5). So a catalyst is heated in shorter period.