• 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.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.39-46
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• 2006

As an automobile fuel, LPG has many environmental advantages compared to gasoline or diesel. However, current LPG engine which is provided with LPG fuel as gas form has lower power and worse fuel efficiency than gasoline engine. These problems of low power and bad fuel efficiency come from lower volumetric efficiency. Also there is a new rising problem of high failure ratio in an engine emission test. Although there are many factors which affect engine performance of exhaust gas emission, one believes that the fact that ECM of gasoline engine is used for LPG engine when retrofitting gasoline engine to LPG engine is one of the main problems, which lower engine power and emit more noxious gas due to wrong ignition timing. To solve these problems, one studied the effects of ignition timing on the exhaust gas to find out the optimum condition of ignition timing. The experimental results show that noxious exhaust gas is reduced and engine power is increased if the optimum control of ignition timing is applied in accordance to the revolution speed of engine.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.3
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• pp.31-44
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• 1987

Nowadays, the problems of energy and environmental pollution become serious day by day and the diesel engine, which has been proved to be superior to gasoline engine with respect to fuel consumption and ecological problems of exhaust gas, has been adopted widely for various purposes from the marine diesel engine and the dynamo engine to all kinds of engine on land. Therefore, extensive parametric studies on combustion of diesel engine should be done for its desing and improvement. To predict the behavior of diesel engien according to variable operating conditions by means of cycle simulation, the reasonable pattern of heat release rate has to be asumed. But it is necessary to know the actual variation of heat release rate in order to assume the reasonable pattern of heat release rate according to the actual operating conditions. In this paper, on a high speed small bore diesel engine with pre-combustion chamber, experimental investigations were carried out to determine the relationship between the heat release pattern and parameters such as engine load and speed. And also, the theoretical investigations about the performance variations of the above diesel engine according to the predicted pattern of heat release rate variation were performed. From the above observations, it may be said that the Fanboro indicator, which was used to get the cylinder pressure, can be used to estimate a reasonable pattern of heat release rate and it is confirmed that the pattern of heat release rate for the pre-combustion type engine is different from that of the direct injection type engine.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.13-20
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• 2014

It is necessary to design a compressor with high pressure ratio that satisfies the IMO(international maritime organization) NOx emission regulation for the marine diesel engine. Impeller was designed using the modified slip factor with the flow coefficient. The main purpose of this study is to investigate the sensitivity of the compressor performance by the vaned diffuser geometries. The first vaned diffuser type was based on a NACA airfoil, the second was channel diffuser, and the third was conformally transformated configuration of a NACA65(4A10)06 airfoil. The sensitivity of the performance was calculated using a commercial CFD program for three different diffuser geometries. The channel diffuser showed the wide range of operation and higher pressure characteristics, comparing with the others. This is attributed to the flow stability at diffuser. Combined with this results with impeller design, the optimized compressor was designed and verified by the test results.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.1-9
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• 2020

Using kerosene and liquid oxygen, 1.5-tonf class liquid-liquid pintle injector with rectangular two-row orifice was designed and manufactured. The combustion test of the pintle injector was carried out to verify the combustion performance and combustion stability under a supercritical condition which is the actual operation condition of the liquid rocket engine. The combustion test result showed that the pintle tip was damaged by the high temperature combustion gas in the high-mixed ratio recirculation zone of the combustion chamber. To solve this problem, the insert nozzle was installed in the pintle injector to increase cooling performance at the pintle tip. As a result of the hot firing test, installation of the insert nozzle, AR and BF had a great effect on pintle tip cooling performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1594-1599
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• 2015

The world car industry is in an era of internal combustion engines in the past 100 years of environmental, energy and IT is eco-friendly, high-tech cars technologies are bringing an era of change. Until now, the study of new technologies in automobile research and development has been focused on. The car's new technology development is also important, but it's cutting-edge technology is used in the car before the car's performance, and became an important point in the customer experience improvement problems. New technology development, as well as effective for existing technology applied is also important. This study was to determine the effects of temperature and the performance of automobile engine and determine the cause of the content in accordance with the type(tap water, distilled water, underground water) of anti-freeze and water that is contained in the automotive engine cooling water for the effective application of the anti-freeze. In the freezing point of the coolant -10, -20, -30, -40, $-50^{\circ}C$ dynamo performance test was conducted with the numerical analysis. Water (distilled water) were measured at the reference point peak performance 71.112, 99.622hp freezing $-10^{\circ}C$.

• Journal of KSNVE
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• v.7 no.4
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• pp.689-700
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• 1997

There are many difficulties in designing the engine structure properly due to the strong conflicts between NVH characteristics and the high performance, light weight and low product cost. Many feasible noise reduction techniques should be carefully incorporated to meet such stringent noise requirements. It is also required that the engine development be carried out by introducing concurrent engineering, in which the analysis and test database are usefully applied to the detail designs from the 1st stage. This paper reviews the significance of the noise characteristics of the structure elements in relation to the combustion pressure. The mechanisms of the crank shaft rumbling, which is the main source having the bad influence on the sound quality, are also explained. The influences of dynamic behavior of engine structure on its noise are investigated, followed by discussions on experimental results of the features necessary for the design of low noise engine concepts.

• Journal of Power System Engineering
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• v.6 no.3
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• pp.11-16
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• 2002

This paper describes the power performance and emission characteristics of the high speed direct injection diesel engine (2.9 litter displacements) driven by soybean oil asknown a bio diesel fuel. The results were compared to diesel fuel with blending bio diesel fuels. The soybean bio diesel fuel was added in the diesel fuel in concentration varying from 25% to 75% volume rates. We measured the emissions according to ECE 13 mode and full load, fixedengine speed. When the 25% bio diesel fuel was used, NOx emission at the ECE 13 mode test slightly decreased compared with diesel base engine. Over engine speed of 2000 rpm, the level of unburned hydrocarbon(HC) and carbon monoxide(CO) were the same to the diesel engine. Smoke emission decreased asthe blending bio diesel fuel rate increased.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.5
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• pp.554-564
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• 2002

A newly designed combustion chamber of diesel engine with a modified piston crown was prepared for the purpose of investigation for reduction of NO emission. It was intended to realize 2-stage combustion that is to keep fuel rich condition during early stage of combustion and fuel lean condition during next stage. The engine was tested on various conditions concerning exhaust gas emissions especially about NO emission and simultaneously fuel consumption rate. It was found that the engine with 2-stage combustion type piston emits significantly low NO at various speed and torque compared with conventional engines, but it raised points at issue in CO and smoke emissions with fuel consumption rate. The increasing of injection pressure on 2 stage combustion type diesel engine affects on CO and smoke emission considerably to reduce but slightly on NO to increase. The effect of 2-stage combustion was better at low speed than at high speed.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.1
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• pp.25-32
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• 1999

This study was carried out to reduce NOx emissions from diesel engine and to investigate the variation of engine performance using the water injection. In this study the water was extracted from the exhaust gas and injected directly into the intake port with the inlet charge. The water condensing system operated as a closed system without any supplementary water supply. The experimental parameters such as the revolution the torque and the water injection rate are varied and the result from this experiment found the significant NOx reduction whereas the smoke emission increases as water/air ratio increases as the cases like the EGR. In spite of increasing the quantity of the water injection the engine output was slightly decreased and the specific fuel consumption was increased as was anticipated. Especially the system was founded to be effective on the reduction of the NOx emissions at the high load region relatively.