• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.78-83
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• 2011

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its high thermal efficiency and lower harmful emissions, including $CO_2$. Although the high octane value of natural gas increases engine output and efficiency due to the high compression ratio, this fuel is prone to such difficulties as a narrow limit of inflammability and a slow combustion speed in the lean burn operation domain, leading to unstable combustion and higher emissions of harmful exhaust gases. Hydrogen blended with natural gas can extend the lean burn limit while maintaining stable, efficient combustion and achieving lower NOx, hydrocarbon and green house gas emissions. In this study, the effect of hydrogen addition on an engine performance and NOx emission characteristics was investigated in a heavy duty natural gas engine. The results showed that thermal efficiency was increased and NOx emissions were reduced due to the expansion of lean operation range under stable operation. NOx emission can be significantly reduced with the retard of spark advance timing.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.42-48
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• 2003

LPG has been a broad concern of pro-environmental alternative fuel for vehicles. Recently, the new Liquid Phase LPG Injection(LPLI) system extends the limit of power of LPG engine and gives a chance to substitute LPG engine for diesel engine of heavy duty vehicles that are the main resources of air pollution in urban area. Large bore size of heavy duty LPG engine derives a serious knock problem. To find an optimal MBT conditions, it is necessary to know how the flame develops in the combustion chamber and find where the knock positions are. In this study. the ion-probe head gasket was used to estimate the knock position. Inverse operation of the ion-probe signal provides the flame developing characteristics. The further the position is from the spark plug, the later the flame arrives and the more times knock occurs. The main factor that effects knock position is inferred a flor situation of mixed gas in the combustion chamber.

• Journal of the Korean Institute of Gas
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• v.14 no.4
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• pp.12-17
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• 2010

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its high thermal efficiency and lower harmful emissions, including $CO_2$. However, the possibility of partial burn and misfire makes the benefits of natural gas fueled engine worse under lean burn operation condition, Hydrogen addition can promote the combustion characteristics while reduces emissions extremely. In this study, the effect of hydrogen addition on an engine performance was investigated. The results showed that thermal efficiency was increased due to the expansion of lean operation range under stable operation. NOx emission can be significantly reduced with the small increase in HC or CO emissions.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.896-902
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• 2001

To meet strict emission regulation while improving engine performances, common rail injection system which is suitable for electronic control, and capable of controlling injection quantity, timing, rate and pressure individually as well as realizing high pressure has been developed. At present study, a 8L DI diesel engine was converted to a single-cylinder experimental engine allowing optical access through an extended piston and a prototype of common rail injector in progress was applied to the engine. The combustion characteristics of the engine were analysed by using direct images and characteristics of the injector were analysed. We can not say that the results are always the same to general common rail injection system but that they are just characteristics of specific prototype injector.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.11-18
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• 2012

대형 상용 엔진에서 발생하는 유효 도시 마력의 약 4~15%는 마찰 손실을 통해서 사라지며 마찰 손실 중 약 40~55%는 엔진 실린더와 피스톤 사이의 마찰에 의하여 발생하여, 엔진 전체에서 발생하는 마찰 손실 중 가장 많은 부분을 차지하고 있다. 이 연구에서는 엔진 실린더 라이너의 온도 분포 개선을 통해 라이너를 따라 유막을 형성하고 있는 윤활유의 적정 점성을 유지시키는 방법을 제시하고자 한다. 피스톤-라이너에서 발생하는 마찰 특성은 피스톤의 행정 위치에 따라서 접촉 마찰과 유막에 의한 마찰로 구분되며 이에 따라 요구되는 윤활유의 점성 특성 또한 달라진다. 먼저 해석 모델을 통하여 실린더 라이너 내부 온도 분포 특성을 확인한 후 피스톤 마찰 특성을 고려한 적정 온도 분포를 고찰하며 실린더 라이너에 열저항 코팅을 통해서 이를 구현하였다. 또한 실린더-피스톤 간의 마찰/윤활 해석을 통하여 열저항 코팅의 마찰 개선효과를 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.784-787
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• 2006

Even if EGR is known as a technology which dramatically reduces NOx emission, its application is a quite complicate since it affects fuel economy and increase of PM emission. Therefore, it is a very important issue to investigate an optimal EGR rate considering all engine parameters. This research was numerically conducted to predict combustion and emission characteristics with respect to various EGR rates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.611-614
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• 2008

Urea-SCR system has been known so far as one of effective after treatments for the reduction of NOx. In order to achieve better performance in SCR system, optimal geometric conditions for a urea injection system should be achieved. This research focused to visualize spray characteristics of urea injected SCR system in a heavy duty diesel engine. The experiment was conducted by varying injection pressures and flow rates of urea. The flow visualization was made by photographing techniques of CCD camera.

• Clean Technology
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• v.22 no.4
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• pp.211-224
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• 2016

Three way catalyst has been used extensively for the exhaust gas treatment for the internal combustion gasoline engine. While, numerous research efforts have been directed to develop various technologies for the abatement of exhaust gas from diesel engine. Diesel engine operating under lean condition produces large amount of NOx and the corresponding catalytic technology employing vanadium supported titania using ammonia has been commercialized for heavy duty vehicle. Recently, the Cu catalyst supported on zeolite has been investigated for NOx abatement using ammonia because of its critical importance for ultra low emission vehicle. The current review shows the recent trend in research and development for zeolite based copper catalysts, which are mainly used as catalysts for selective catalytic reduction using ammonia, are one of the aftertreatment technologies for effectively removing nitrogen oxides from diesel exhaust.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.29-36
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• 2015

This study is an 1-D numerical study prior to modification of diesel engine for power plants to natural gas/diesel dual fuel engine using GT-Power with 1.5MW diesel engine for power generation. Natural gas injector was installed to intake manifold for dual fuel engine model. Effects on engine performance and characteristics were investigated when dual fuel is used in unmodified diesel engine. The analysis was done under 5 conditions from 0% to 40% of mixing rate on 720RPM engine speed. As a result of research, the engine performance was decreased as increasing ratio of natural gas. Engine brake power was decreased by 18.4% under 40% mixing rate condition. To clarify the reason, effects of injection timing and period were evaluated with DOE method. Considering this result, optimization was done for these parameters. Also, comparison between performances of dual fueled engine and diesel engine was made after optimizing the timing of injection by DOE method. As a result, engine brake power was decreased by 8.55% under mixing rate 40% condition showing 12.5% improvement.