• 한국자동차공학회논문집
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• 제2권5호
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• pp.30-40
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• 1994

The direct-injection stratified-charge engine has the advantages of higher thermal efficiency and less CO and $NO_x$ emission levels than conventional spark ignition engines. However, its actual utilization is prevented by high unburned hydrocarbon emission levels during light-load operations. In this paper, fundamental studies were carried out using a pancake type constant volume bomb. The effects of intensification of local premixing by tangential and radial fuel injection were examined experimentally. Unburned hydrocarbon emission levels with radial fuel injection were shown to be lower than those of tangential fuel injection cases. The stratification and mixing process of fuel jet and combustion process were observed by schlieren photography.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.212-219
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• 1998

Unburned hydrocarbon is a key contributor to both the fuel economy and emissions of automotive engine. Cyclic variation of HC emission is of importance, especially during throttle transients. The real time measurement of hydrocarbon is particularly important to obtain a better understanding of the mechanisms for combustion and emissions, especially during cold start and throttle transient condition. This paper reports the cycle resolved measurement technique of unburned hydrocarbons to quantify rapid changes of in-cylinder concentration in the vicinity of spark plug by using the Fast Response Flame Ionization Detector(FRFID). While this instrument actually measures fuel concentration, its results can be indicative of the AFR behaviour. In order to understand the rapid change of hydrocarbons with cylinder pressure, it is necessary to study the response time delay of the system, including the time associated with gas transportation to FID. And signal from FRFID is correlated with cylinder pressure data to relate changes in mixture preparation to the classic analysis, such as indicated mean effective(IMEF) and ignition delay, etc.

• 한국자동차공학회논문집
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• 제8권2호
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• pp.33-40
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• 2000

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, a numerical simulation was performed with 3-dimensional flow model and oxidation mechanism optimized for port oxidation. To predict the exhaust and oxidation process with consideration of flow, mixing, and temperature, 3-dimensional flow model and HC oxidation model were used with a commercial computational program, STAR-CD. The flow model were with moving grid for valve motion, which could predict the change of flow field with respect to valve lift. Optimization was performed to predict the HC oxidation with temperature range of 1200~1500K, low HC and oxygen concentration, existence of intermediate species, as typical in port oxidation. The constructed model could predict the port oxidation process with oxidation degree of 14~48% according to the engine operation conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.150-155
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• 2000

Exhaust emissions from vehicles are the main source of air pollution. Many researchers are trying to find the way of reducing vehicle emissions, especially in the cold transient period of the FTP-75 test. In this study, UEGI (Unburned Exhaust Gas Ignition) technology, warming up the close-coupled catalytic converter (CCC) by igniting the unburned exhaust mixture using two glow plugs installed in the upstream of the catalyst, was developed. It was applied to an exhaust system with a hydrocarbon adsorber to ensure an effective reduction of HC emission during the cold start period. Results showed that the CCC reaches the light-off temperature (LOT) in a shorter time compared with the baseline exhaust system, and HC and CO emissions are reduced significantly during the cold start.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.888-895
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• 2003

Combustion chamber crevices in SI engines are identified as the largest contributors to the engine-out hydrocarbon emissions. The largest crevice is the piston ring-pack crevice. A numerical simulation method was developed, which would allow to predict and understand the oxidation process of piston crevice hydrocarbons. A computational mesh with a moving grid to represent the piston motion was built and a 4-step oxidation model involving seven species was used. The sixteen coefficients in the rate expressions of 4-step oxidation model are optimized based on the results from a study on the detailed chemical kinetic mechanism of oxidation in the engine combustion chamber. Propane was used as the fuel in order to eliminate oil layer absorption and the liquid fuel effect. Initial conditions of the burned gas temperature and in-cylinder pressure were obtained from the 2-zone cycle simulation model. And the simulation was carried out from the end of combustion to the exhaust valve opening for various engine speeds, loads, equivalence ratios and crevice volumes. The total hydrocarbon (THC) oxidation in the crevice during the expansion stroke was 54.9% at 1500 rpm and 0.4 bar (warmed-up condition). The oxidation rate increased at high loads, high swirl ratios, and near stoichiometric conditions. As the crevice volume increased, the amount of unburned HC left at EVO (Exhaust Valve Opening) increased slightly.

• 대한기계학회논문집B
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• 제34권4호
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• pp.417-422
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• 2010

1.7L 커먼 레일 직접 연료분사 디젤엔진과 초저유황 스웨덴 디젤 연료를 이용하여 연료분사시기 8.5CA BTDC~0.5CA BTDC 와 배기가스 재순환률 37%, 43%, 48% 영역에서 실험을 수행하였다. 각각의 배기가스 재순환률에 대하여 연료분사시기가 지각됨에 따라 매연과 질소산화물이 동시에 저감되나 탄화수소와 일산화탄소는 증가하는 저온 디젤 연소영역에 있음을 확인하였다. 탄화수소를 가스크로마토그래프와 불꽃 이온 검출기를 사용하여 종 분석을 수행하였으며, 연료분사시기가 지각될수록, 그리고 배기가스 재순환률이 증가할수록 Partially burned HC, 알켄의 비율이 증가하였다. Partially burned HC 중에서 에텐이, 그리고 Unburned HC 중에서 노말 운데케인이 가장 많이 배출되었다. 이 두 개의 탄화수소 종은 촉매 연구에 사용되는 벤치 플로우리액터 시험에서 대표적인 탄화수소 종으로 사용할 수 있다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.39-47
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• 2003

UEGI (Unburned Exhaust Gas Ignition) is an alternative method for fast light-off of a catalyst. It ignites the unburned exhaust mixture using two glow plugs installed in the upstream of the close-coupled catalysts. In addition, a hydrocarbon adsorber was applied to the UEGI, for more effective reduction of HC emission. Engine bench tests show that the CCC reaches the light-off temperature laster than the baseline exhaust system and HC and CO emissions are reduced significantly during the cold start. From the vehicle test, it was observed that a few amount of HC emission was reduced even the catalysts were aged. It is expected to develop a solution kit applicable to a new vehicle or used one, to meet the emission regulation

• 한국자동차공학회논문집
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• 제11권2호
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• pp.1-7
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• 2003

This paper proposes a method to detect misfired cylinders by the exhaust pressure ascent rate. The misfire is generated by faults of electric system or faults of fuel delivery system. It is one of the abnormal combustions. Therefore, it increases the unburned hydrocarbon and the carbon monoxide and affects a bad influence to the 3-way catalyst. The misfire causes to decrease the power of the engine and increase the consumption of the fuel. Early detection and correction of the misfired cylinders can prevent these unusual phenomena. The misfired cylinders can be detected by the comparison of exhaust pressure ascent rate during each cycle. The exhaust pressure ascent rate is defined as pressure rise per time. Our experimental results showed that the proposed method is effective in the detection of the misfired cylinders on a gasoline engine regardless loads and revolutions of the engine.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.46-57
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• 1996

The direct injection stratified charge(DISC) engine enhances the fuel tolerance and the antiknock tendency. This enhanc3d antiknock tendency allows use of a higher compression ratio which results in higher thermal efficiency. But its actual utilization is prevented by high emission combustion time and wall quenching will be the main causes of increasing unburned hydrocarbons in DISC system. In order to solve this problem, small aount of hydrogen was added to the charging air or injected fuel. The effects of hydrogen addition were examined experimentally by radial fuel injection using a pancake-type constant volume bomb. In case of the hydrogen addition to the charge of air, the combustion the amount of hydrogen. In case of the hydrogen addition to the fuel, the combustion pressure was significantly increased.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.17-23
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyze the heat quantity of homogeneous charge methane-air mixture under various initial pressures, excess air ratios and ignition times. As the overall pressure increase, the values of maximum combustion pressure, maximum heat release rate and cumulative heat release have been increased. But it is not very meaningful to compare with some values such as maximum combustion pressure, maximum heat release rate and cumulative heat release for different overall pressure due to the different heat energy of supplied fuel. So the each value is needed to be compared with normalized value, which is divided by the entered fuel energy. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. As the overall pressure increase, the CHR ratios and the UHC ratios have been decreased, while the HL ratios have been increased. The CHR ratio of 300 ms has the higher value than that of 10000ms, and the HL ratios of 300 ms have a lower value.