• Journal of Power System Engineering
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• v.22 no.1
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• pp.56-63
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• 2018

After the recent fabrication of diesel vehicle exhaust gas by Volkswagen, nitrogen oxides ($NO_x$) and particulate matter (PM) are drawing attention as representative pollutants included in exhaust gas. When gasoline and diesel fuels are combusted through direct injection into a combustion chamber at high pressure, PM emission is actually increased. To find a solution to this problem, a basic study was conducted to derive an optimized variable for combustion of compressed natural gas (CNG) by applying CNG, acknowledged as a clean fuel, to direct injection system. The essence of this study is in the introduction of a radical ignition technology for compressed natural gas (RI-CNG) in a sub-chamber type engine. The direct injection system was applied to a sub-chamber to remove residual gas from previous combustion cycle. In addition, optimal mixer distribution was achieved by precisely setting ignition timing based on fuel injection timing and excess air ratio.

• 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 the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.106-111
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• 2006

Combustion test facility for liquid rocket engine using kerosene and liquid oxygen has been developed for the purpose of cooling and performance study. Test engine of thrust under 1.0 KN can be evaluated, and the real combustion test ensures a good operation of the combustion test facility. Combustion test facility will be modified to supply natural gas and liquefied natural gas as fuel and to give a regenerative cooling test.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.9-12
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• 2007

In this study, a new method of combustion characteristics have been proposed to reduce exhaust emissions in a diesel engine using four kinds of mixed fuel. Mixed fuels show four different torque ratios between diesel oil md natural gas, which are 4:0, 3:1, 2:2 and 1:3. In order to investigate the exhaust gas during combustion, exhaust gases are sampled by gas analyzer, for example NOx, Soot, CO, and HC, as the RPM changed. As a result, the NOx, CO, and HC concentrations of mixed fuel are higher than those of diesel oil only. However, the Soot concentration of mixed fuel is lower when diesel oil is burned.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1591-1602
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• 1996

In operating the underwater engines such as encountered in exploring submarines, the dumping of the exhaust gas out of the engine requires a large portion of the total power, frequently amounting to 25-30% of the power generated. This unfavorable circumstance can be cured by liquefying the exhaust gas and storing it. In the present study, two liquefaction systems were simulated to enhance the overall efficiency; one is a closed cycle diesel engine and the other is a closed cycle LNG engine. The liquefied natural gas (LNG) is chosen as a fuel, not only because its use is economical but also because its cold energy can be utilized within the liquefaction system. Since a mixture of oxygen and carbon dioxide is used as an oxidizer, liquefying carbon dioxide is of major concern in this study. For further improving this system, the intercooling of the compressor is devised. The necessary power consumed for the liquefying system is examined in terms of the related properties such as pressure and temperature of the carbon dioxide vessel as a function of the amount of the exhaust gas which enters the compressor. The present study was successful to show that much gain in the power and reduction of the vessel pressure could be achieved in the case of the closed cycle LNG engine. The compression power of exhaust gas were observed remarkably lower, typically only 6.3% for the closed cycle diesel engine and 3.4% for the closed cycle LNG engine respectively, out of net engine power. For practicality, a design -purpose map of the operating parameters of the liquefaction systems was also presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.155-164
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• 1996

Dual-fuel engines are being researched with emphasis on the possible types of natural gas supply systems. Hence, a three-dimensional combustion model by using finite volume method was developed to provide a fundamental understanding of the auto-ignition of pilot distillate and subsequent burning of natural gas, when the natural gas as well as the distillate was directly injected into a quiescent diesel engine like combustion bomb tests and the numerical results were investigated for the mixed combustion phenomena. With high-pressure natural gas injection, it was found that the gaseous fuel injection characteristics had to be well harmonised with that of the pilot distillate. For better combustion efficiency, however, further researches are required for the optimisation of injection system in the existence of air motion.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.11a
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• pp.213-218
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• 2004

• Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.20-23
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• 2009

The structural analysis of liquid rocket engine was performed in the case of sinusoidal vibration load to verify structural safety. The finite element model is composed with main liquid rocket engine components, combustion chamber, turbopump, gas-generator, pyro-starter, main pipes, main valve, heat-exchanger, gimbal-mount and brackets. Natural vibration mode analysis and structural analysis for sinusoidal vibration load were performed. The natural mode frequency of liquid rocket engine is twice than that of launch vehicle. In the case of stress result of sinusoidal vibration load, the part of maximum stress has 1.4 margin, so the engine structure is safe for sinusoidal vibration load.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.911-917
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• 2013

This is a thesis about the experiment of comparison characteristic of power and exhaust gas in the same condition between diesel engine that is equipped response power 220HP turbocharger to increase effectiveness of the engine which is recently used in a lot of industry which requires high power. Resulting of the experiment with natural aspiration diesel engine and turbocharger diesel engine, difference in low speed is not significant, but in high speed, effectiveness of turbocharger diesel engine is much higher than the other one. In other hand, in exhaust gas experiment, turbocharger model exhausts more $NO_X$ and $O_2$, but it doesn't significantly affect the result when it comes with decreasing of $CO_2$ and effectiveness of increased power characteristic. As a result, the turbocharger diesel engine is economically effective comparing with the natural aspiration diesel engine.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.198-203
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• 2008

The objective of the research was to study the effects of Miller cycle in a modified using diesel engine. The engine was dedicated to natural gas usage by modifying pistons, fuel system and ignition systems. The engine was installed on a dynamometer and attached with various sensors and controllers. Intake valve timing, engine speed, load, injection timing and ignition timing are main parameters. The results of engine performances and emissions are present in form of graphs. Miller Cycle without supercharging can increase brake thermal efficiency and reduce brake specific fuel consumption. The injection timing must be synchronous with valve timing, speed and load to control the performances, emissions and knock margin. Throughout these tested speeds, original camshaft is recommended to obtain high volumetric efficiency. Retard ignition timing can reduce $NO_x$ emissions while maintaining high efficiency.