• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1151-1158
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• 2000

Combustion analysis based on cylinder-pressure provides a mechanism through which a combustion researcher can understand the combustion process. The objective of this paper was to identify the most significant sources of cycle-to-cycle combustion variability in a spark ignition engine at idle. To analyse the cyclic variation in a test engine, the burn parameters are determined on a cycle-to-cycle basis through the analysis of the engine pressure data. The burn rate analysis program was used here and the burn parameters were used to determine the variations in the input parameter-i. e., fuel, air, and residual mass. In this study, we investigated the relationship of indicated mean effective pressure (IMEP), coefficient of variation (COV) of IMEP, burn angles, and lowest normalized value (LNV) in a spark ignition engine in a view of cyclic variations.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.4
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• pp.72-79
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• 1994

In an automotive spark ignition, it is important to form the proper mixture(air/fuel) on each driving condition for developing the stabilizing combustion and exhaust characteristics. Since most of supply fuel is attached on the inside wall of the intake manifold for unadequate atomization by fuel injection system, it brings a bad effect on combustion and exhaust caused by nonuniformity of fuel distribution to each cylinder and mixture variation. Also it affects engine performance variation and causes noises and vibration. In this study, we verified the effect of the mixture variation which is caused by fuel liquid film in an intake manifold on combustion characteristics and engine performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.87-95
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• 2009

EGR(Exhaust gas recirculation) provides an important contribution in achieving the development targets of low fuel consumption and low exhaust emission levels on gasoline engine for hybrid vehicles while allowing stoichiometric fuelling to be retained for applications using the three-way catalysts. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate in gasoline engine for hybrid vehicles should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR with optimum EGR rate on fuel economy, combustion stability, engine performance and exhaust emissions. As the engine load becomes higher, the optimum EGR rate tends to increase. The increase in engine load and reduction in engine speed make the fuel consumption better. The fuel consumption was improved by maximum 5.5% at low speed, high load operating condition. As the simulated EGR variation on a cylinder is increased, due to the increase in cyclic variation, the fuel consumption and emissions characteristics were deteriorated simultaneously. To achieve combustion stability without a penalty in fuel consumption and emissions, the cylinder-to-cylinder variations must be maintained under 10%.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.2
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• pp.138-144
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• 2007

The variation of the crankshaft speed in a multi-cylinder engine is determined by the resultant gas pressure torque and the torsional deformation of the crankshaft. Under steady state operation, the crankshaft speed has a quasi-periodic variation. For the diagnosis the engine instantaneous speed versus crankshaft angle is utilized. This paper describes a simple measurement method of the engine instantaneous speed versus crankshaft angle using the teeth on the flywheel of the crankshaft. Two non-contacting magnetic pickup combinations detect the crank angle and TDC position for the data acquisition. The results from experiments on a 6 cylinder marine diesel engine demonstrate that the crankshaft speed variation are detected with good resolution. And the crankshaft speed variation is investigated according to the operation conditions. Also, it is confirmed that the engine output measured by EMS can be evaluated larger than the actual value due to TDC position error caused by instantaneous speed variation.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.45-50
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• 2000

A numerical investigation is made of three-dimensional buoyant convection of a Boussinesq-fluid in a vertical cylinder. The top and bottom endwalls are thermally insulated. Flow is driven by the substantial azimuthal variations in thermal boundary conditions. Comprehensive numerical solutions to the Navier-Stokes equations are obtained. The representative Rayleigh number is large, thus, the overall flow pattern is of boundary layer-type. Three-dimensional (low characteristics are described. Specially, the global flow and the heat transfer features are delineated when the severity of azimuthal variation of sidewall temperature n, is intensified. Temperature and velocity fields on the meridional planes and the planes of constant height are presented. The global flow weakens as n becomes large. The pattern of the local Nusselt number on the surface of cylinder is similar regardless of n. The convective gain in heat transfer activities is reduced as n increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.40-49
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• 1994

This paper describes the method to investigate combustion pressure in the cylinder without modifications of engine. Assuming engine dynamics as a single degree of freedom cylinder pressure is estimated using the variation of crank shaft speed. For this study pressure, crank shaft sped, and load are sampled by the crank angle. This study suggests the variation of crank shaft speed can be used as parameters of feedback engine control.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.66-73
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• 2004

This paper presents characteristics of combustion and exhaust gas properties according to variation of the combustion chamber for economy and emissions standards. In order to use combustion and exhaust gas properties data, it is necessary to build some data base, which use cylinder pressure sensor and emission tester. A feasibility and necessity of combustion pressure based cylinder spark timing control has been examined. So, this was obtained the coefficient of variation(COV) and the specific fuel consumption(sfc). Using the results of the test, the effects of the variable combustion chamber can be improved combustion stability and be reduced exhaust emission.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.2
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• pp.41-54
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• 1989

In this study, steady state heat conduction problems of the cylinder block of turbocharged gasoline engine were solved by the boundary element method. Surface of the cylinder block was divided by the triangular cells with constant potential. Temperature distribution, effective heat transfer coefficient of the cylinder block were investigated with variation of equivalence ratio, engine speed and boost pressure. The results show that maximum temperature of cylinder block increase rapidly with increasing engine speed and boost pressure. The monolithic structure of cylinder block results in sever inhomogeneity of inner wall temperature at the high engine speed and boost pressure.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.75-82
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• 2004

In this research, a computer analysis has been developed for predicting the Pipe pressure of the intake and exhaust manifold in a small single cylinder engine. To get the boundary conditions for a numerical analysis one dimensional and unsteady gas dynamic calculation is performed by using the MOC(Method Of Characteristics). The main numerical parameters are engine revolutions. to calculate the Pulsating flow which the intake and exhaust valves are working. The distributions of the exhaust pipe pressures were influenced strongly to the cylinder pressures and the shapes of exhaust pressure variation were similar to the Inside of cylinder pressure As the engine revolutions are increased. the intake pressure was lower than ambient pressure. The amplitude of exhaust pressure had increased and the phase of cylinder pressure $P_c$ is delayed and the amplitude of cylinder pressure were increased.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.181-210
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• 1997

The stress distribution generated in the surrounding bone was calculated and compared for various geometry of the dental implants by means of the finite element methods. The models were designed to represent the screw type endosseous implants(varing the size, shape, direction of the screw thread and the angle of the body) with supporting bone and the cylinder type endosseous implants(varing the lower portion-Round type, tapered type) with supporting bone. Static mean bite forces were applied 100N vertically and 25N horizontally on the center of the implant and three dimensional finite analysis was undertaken using software ANSYS 5.1 Version. The result demonstrated that different implant shape leads to significant variations in stress distribution in the bone. In the case of variation of the screw size, direction and shape the implant model with normally directional and triangular screw implied lower stress than with upper directional or lower directional and quadrangular screw but among models a different screw size, within a variation of 0.2mm there was no meaningful difference in maximum stress. In the case of variation of angle of body the straight implied lower stress than the tapered. As a result of analysis of cylinder type, the implants with larger radius of curvature of the round form and larger diameter of the tapered form implied lower stress.