• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.837-844
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• 2014

Automotive manufacturers have recently developed various technologies for improving fuel economy and satisfying enhanced emission regulations. The ultra-lean direct injection engine is a promising technology because it has the advantage of improving thermal efficiency through the deliberate control of ignition. A conventional LPG engine has been redesigned to an ultra-lean-burn LPG direct injection engine in order to adopt combustion system of ultra-lean-burn. This study is aimed at investigating the effect of a change in the compression ratio on the performance and emission characteristics of a lean-burn LPG engine. The fuel consumption, heat release rate, combustion pressure, and emission characteristics are estimated depending on changing the effect of compression ratio. When the compression ratio is increased, it is difficult to improve the fuel consumption owing to an unstable combustion state, but the total hydrocarbon and nitrogen oxide emissions are reduced.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.2
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• pp.118-124
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• 2007

The oceans could absorb almost all the anthropogenic carbon dioxide the mankind has been producing eventually, but in the nature the air-sea $CO_2$ exchange occurs very slowly and to lower the atmospheric $CO_2$ concentration substantially $CO_2$ must be injected to the interior of the ocean directly. If we inject $CO_2$ collected at the major $CO_2$ sources into the international waters in the Philippine Sea or east of Japan, we could store the $CO_2$ in the oceans effectively for a few hundred years. When $CO_2$ is dissolved into the water, PH drops. The creatures adapted to the deep oceans where environment is very stable could be affected by even a small change in pH significantly. If, therefore, we are to inject $CO_2$ into the oceans, we must assess the effect of $CO_2$ injection in the marine ecosystem beforehand. Only when the damage to the marine ecosystem is smaller than the benefit from the $CO_2$ injection, $CO_2$ injection is effective.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.643-647
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• 2014

Two types of fuel supply method ar used in CNG vehicles. One is premixed ignition and the other is gas-jet ignition. In premixed ignition, the fuel is introduced with intake air so that homogeneous air-fuel mixture may form. The ignitability of this method depends on the global equivalence ratio. In gas-jet ignition, CNG is introduced directly into the engine combustion chamber. The overall mixture is stratified by retarded fuel injection. In this study, a visualization technique was employed to obtain fundamental properties regarding overall mixture formation of direct injected CNG fuel inside a constant volume chamber. Jet angles, penetrations and projected jet area with respect to ambient pressure are investigated. The penetration decreases apparently and the time reaching the CVC wall was delayed as the chamber pressure increases. This is caused by the higher inertia of the fluid elements that the injected fluid must accelerate and push aside. It is same to liquid fuel such as diesel and gasoline, but this phenomenon is far more prominent for the gaseous fuel.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.44-51
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• 2005

According to the increasing concern on the global environment, the $CO_2$ regulation has been discussed including automobile emission regulation. In order to cope with this rapid changing circumstances, the development of an ultra low emission and super fuel economy automobile is essential. Direct injection LPG engine is the one of the possible future engine to maximize the engine efficiency. This experimental study for the development of direct injection LPG engine technology is promoted with two parts; spray characteristics of high pressure swirl injector, and performance characteristics of direct injection LPG engine. Engine characteristics according to the fuel was analyzed in order to establish stratified combustion technology for LPG engine by using the DISI engine. In the engine experiment, control system was manufactured for gasoline and LPG fuel. The engine was modified 2,000 cc GDI engine (fuel supply device, fuel injection device). Through this experiment, engine operating condition, engine speed and spark timing (MBT), fuel injection position, and fuel rate were investigated.

• Journal of ILASS-Korea
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• v.21 no.3
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• pp.121-129
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• 2016

The advantages of the common rail fuel injection system architecture have been recognized since the development of the diesel engine. In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure up to and above 2000 bar. And solenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomization. In this study, the direct needle-driven piezo injector was investigated for accomplishing injection pressure of 1800 bar by optimal design by simplification of component and changing number of springs and plates of DPI. It was found that a direct needle-driven piezo injection system features the prototype DPI for passenger vehicle to operate at 1800 bar of injection pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.39-45
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• 2012

Today gasoline engines for vehicular application are not only faced with stringent emission regulation but also with increasing requirements to better fuel economy, while guaranteeing power density. The spray-guided type gasoline direct injection (GDI) engine has an advantage of improved thermal efficiency and lower harmful emissions. Centrally mounted high pressure injector and adjacent spark plug allow stable lean combustion due to the flexible mixture stratification. In the present study, the performance and emissions characteristics of developed spray-guided type GDI combustion system were evaluated at various excess air ratio conditions. The specific fuel consumption and nitrogen oxides ($NO_x$) emissions were reduced due to the achievement of stable lean combustion under flammability limit. Multiple injection strategy was not helpful to improve fuel consumption while further reduction of $NO_x$ emissions was possible.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.144-152
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• 2006

Split injection has been known to reduce total hydrocarbon (THC) emission level and increase engine performance under certain operating conditions 1, 2). Exhaust Gas Recirculation (EGR) is a common technique adopted for nirtric oxides (NOx) reduction by the dilution of intake air, despite a sacrifice of simultaneous increase in THC and decrease in engine performance3). Thus, using split injection with adequate EGR may improve the emission level of UBHC, NOx and the engine performance compared to that of single-injection with or without EGR cases. The purpose of this study is to investigate the engine performance and emission levels at various engine operating conditions and injection methods when it is applied with EGR. The characteristics of single-injection and split-injection were investigated with various engine loads and EGR rates. The engine speed is changed from 800rpm to 1200rpm to investigate how the combustion characteristics are changing with increasing engine speed.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.76-87
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• 2019

A direct connected test was conducted for a supersonic combustor with a cavity-type flame holder. Liquid hydro-carbon fuel was injected in different types of injectors: inclined and aeroramp injectors, for the flow condition of Mach 4 at an altitude of 20 km. The static pressure on the combustor wall along the axis and the total pressure at the exit of combustor were measured to analyze the combustion characteristics at various fuel flow rates.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.1-8
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• 2014

Liquefied petroleum gas (LPG) is regarded as an alternative fuel for spark ignition engine due to similar or even higher octane number. In addition, LPG has better fuel characteristics including high vaporization characteristic and low carbon/hydrogen ratio leading to a reduction in carbon dioxide emission. Recently, development of LPG direct injection system started to improve performance of vehicles fuelled with LPG. However, spray characteristics of LPG were not well understood, which is should be known to develop injector for LPG direct injection engines. In this study, effects of operation condition including ambient pressure, temperature, and injection pressure on spray properties of n-butane were evaluated and compared to gasoline in a multi-hole injector. As general characteristics of both fuels, spray penetration becomes smaller with an increase of ambient pressure as well as a reduction in the injection pressure. However, it is found that evaporation of n-butane was faster compared to gasoline under all experimental condition. As a result, spray penetration of n-butane was shorter than that of gasoline. This result was due to higher vapor pressure and lower boiling point of n-butane. On the other hand, spray angle of both fuels do not vary much except under high ambient temperature conditions. Furthermore, spray shape of n-butane spray becomes completely different from that of gasoline at high ambient temperature conditions due to flash boiling of n-butane.

• 발명특허
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• v.30 no.3 s.345
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• pp.44-46
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• 2005