• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3553-3558
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• 2009

This study has been conducted to improve coolant flow pattern in the gasoline engine. Flow field has been calculated for the coolant passage mainly around the exhaust ports and valves. For the original model, a flow stagnant region has existed between exhaust valves of the second cylinder. To improve coolant flow characteristics, coolant passage area has been re-modeled and optimized. Furthermore, for the improved coolant core model, coolant passage under the exhaust manifold has been added to reduce exhaust-gas temperature. It was found that the flow through a gasket plays a critical role for the flow in the cylinder head and around exhaust valves. Finally, coolant flow around exhaust valves and in the cylinder head has been improved in terms of flow rate distribution.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.893-900
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• 2008

The heat exchangers in the ships have been changed from the conventional shell & tube type to the plate type due to some merits as a compactness, a high thermal efficiency and a light-weight. In recent. it is reported that the vacuum phenomena were occurred in the seawater outlet piping of a main central cooler (MCC) on the ships. From the viewpoints of a common sense, the vacuum pressure in the seawater piping is rare event and difficult to be convinced because the seawater is pumped into the piping by a seawater pump with a high discharge head. However, the occurrence of a vacuum pressure in the seawater line of an MCC is real situation and often gives a severe damage to a rubber gasket of an MCC with a plate type heat transfer area. In this study, we analyzed the vacuum pressure in the seawater line of an MCC by using the simpl Bernoulli's equation and found that the vacuum pressure in the seawater line of an MCC is inevitable untill the installation postion of an MCC is not lowered.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.5-10
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• 2011

The spatial fuel vapor distribution of the homogeneous charge by a 6-hole injector was examined in a optically accessed single cylinder direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF (Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played a little more effective role in the spatial fuel vapor distribution than the swirl flow during the compression stroke at 10 mm and 2 mm planes under cylinder head gasket and the increased fuel injection pressure activated spatial distributions of the fuel vapor. In additions, richer mixtures were concentrated around the cylinder wall by the increase of the coolant temperature.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.155-163
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• 1999

In this study, single cylinder engines with different tumble ratio were made to find out in-cylinder fluid motion and flame propagation. Tumble ratio derived from the steady state flow rig test. Flame propagation speed was obtained using cylinder head gasket ionization probe and the piston ionization probe. And the combustion pressure in cylinder was measured to analyze the combustion characteristics. In case of high tumble engine, BSFC and BSHC were decreased and BSNOx was increased at part load test. Also BMEP and combustion peak pressure was increased at full load test. Tumble flow motion had an great effects on initial burning period rather than main burning period in part load test.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.511-517
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• 2019

Two type pistons which had different configuration were made to find out the effects on combustion and flame propagation. Flame propagation speed was obtained by use of the cylinder head gasket ionization probe. Ionization Probe voltage output and flame propagation speed were increased according to the air fuel mixture ratio increase. Exhaust direction flame propagation speed was fastest in combustion chamber and next was front direction, rear direction and intake direction cause of tumbling motion in cylinder. In case of remove the valve pocket in piston, average flame propagation speed changed slowly and spark timing was advanced. Also emission was decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.8
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• pp.718-723
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• 2007

The new concept spark plug was developed to study its influence on the combustion characteristics of SI engine. It has pre-ignition chamber in the lower end of spark plug and flame hole, in which fresh mixture gas can be introduced without any fuel supply system. This spark plug was tested with a commercial SI engine. Fuel consumption rate, emission gas and MBT timing were measured in the engine dynamometer for various flame hole numbers, hole positions, hole sizes of the pre-ignition chamber of the spark plug. And average flame propagation speed was measured by using the head gasket ionization probe in single cylinder engine. The new concept spark plug induces fast bum in combustion compared with the conventional spark plug, and MBT(Minimum advance for Best Torque) timing was retarded about $3{\sim}5^{\circ}$ crank angle. The flame hole number, hole direction and volume of pre-ignition chamber were found to influence the combustion characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.1-8
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• 2002

Metal surface temperatures around the combustion chamber in a gasoline engine directly affect thermal durability and performance of the engine. Metal surface temperatures are influenced by many cooling factors such as drilled water passage, deflector, combustion chamber wall thickness, pillar, and coolant flow pattern. The object of this study is to learn how the coolant passages and coolant flow pattern in an engine influence to the engine metal surface temperature at engine full load and speed. From the test result, it is suggested a plan to reinforce the engine stiffness and to reduce the thermal stress simultaneously. Also, approaches are introduced to reduce the thermal load on the engine by adjusting the discharging direction from the water pump and by optimizing the water transfer holes in the cylinder head gasket. These methods and the optimized engine cooling system, which were suggested in this paper, were adapted for an engine in progress to eliminate the exhaust valve seat wear.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.5
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• pp.402-410
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• 2008

The heavy duty diesel engine must have a large output for maintaining excellent mobility. In this study, a three dimensional finite element model of a heavy-duty diesel engine was developed to conduct the stress analysis. The FE model of the heavy duty diesel engine main parts consisting with four half cylinder was selected. The heavy duty diesel engine parts includes with cylinder block, cylinder head, gasket, liner, bearing cap, bearing and bolts. The loading conditions of engine were pre-fit load, assembly load, and gas load. As the results of structural analysis, because the stress values of cylinder block and bearing cap did not exceed the basic design can be satisfied. But on the part which contacts with cylinder block and bearing cap the stress value exceeds the allowable strength of material. In order to decrease the stress at that part, it was optimized with parametric study.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.133-139
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• 2005

In this study, a three-dimensional transient simulation with a knock model was performed to predict knock occurrence and autoignition site in a heavy-duty LPG engine. A FAE (Flame Area Evolutoin) premixed combustion model was applied to simulate flame propagation. The coefficient of the reduced kinetic model was adjusted to LPG fuel and used to simulate autoignition in the unburned gas region. Engine experiments using a single-cylinder research engine were performed to calibrate the reduced kinetic model and to verify the results of the modeling. A pressure transducer and a head-gasket type ion-probe circuit board were installed in order to detect knock occurrences, flame arrival angles, and autoignition sites. Knock occurrence and position were compared for different piston bowl shapes. The simulation concurred with engine experimental data regarding the cylinder pressure, flame arrival angle, knock occurrence, and autoignition site. Furthermore, it provided much information about in-cylinder phenomena and solutions that might help reducing the knocking tendency. The knock simulation model presented in this paper can be used for a development tool of engine design.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.145-151
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• 2005

Natural gas is one of clean fuels that can replace petroleum-based fuels, because it has low exhaust emission, comparatively high thermal efficiency and abundant deposits. In this addition, owing to high octane number and wide lean flammability limit, it has a strong point to increase the compression ratio. For this reason, the research is being actively executed to increase the generating power and thermal efficiency of the engine by raising the compression ratio through utilization of high octane number relevant to development of CNG engine. In this study, 0.63L single cylinder diesel engine has been used to alter easily compression ratio. Compression ratio has gotten under control by modifying the thickness of gasket between cylinder head and block without major structural modifications. As the result, as compression ratio has increased, generating power and fuel consumption ratio have been improved. As for emission concentration, as compression ratio has increased, THC concentration has been decreased while exhause concentration of NOx increased. In case compression ratio has excessively increased, brake output decrease and cycle variation have been increased. As the result acquired by analyzing brake output, fuel consumption ratio, cycle variation and exhaust, the engine driving condition has acquired $\varepsilon=13$ as the optimal compression ratio in this study.