• 한국자동차공학회논문집
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• 제19권6호
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• pp.46-52
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• 2011

Homogeneous charge compression ignition (HCCI) is the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. However, HCCI engine's operation have an excessive rate of pressure rising during the combustion process. In this study, stratification condition of EGR exhaust gases was used to reduce the pressure rising during the combustion process in HCCI engine. Also, combustion characteristics and emissions characteristics were investigated using the detailed diesel surrogate reaction mechanism.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.10-16
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• 2004

The Homogeneous Charge Compression Ignition (HCCI) engine has advantage for reducing the NOx and P.M. simultaneously. Therefore, HCCI engine is receiving attention as a low emission diesel engine concept. This study was carried out to investigate the characteristics of combustion and exhaust emission for operating conditions in a direct injection type of HCCI engines such as supercharged and naturally aspirated using diesel fuel and additive. From the experimental result, we found that cool flame was always appeared and also it was difficult to control combustion characteristics by changing the injection timing in HCCI. In addition, at the lean air-fuel ratio and high speed range, it was observed that charging air pressure, additive or increasing intake air temperature is effective to increase combustion performance and reduce exhaust emission. We concluded that chemical reaction by the increasing intake air temperature or additive without physical improvement has limitation for reduction of exhaust emission.

• 대한기계학회논문집B
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• 제30권6호
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• pp.538-545
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• 2006

Stratified charge compression ignition (SCCI) combustion, also known as HCCI(homogeneous charge compression ignition), offers the potential to improve fuel economy and reduce emission. In this study, SCCI combustion was studied in a single cylinder gasoline DI engine, with a direct injection system. We investigated the effects of air-fuel ratio, intake temperature and injection timing such as early injection and late injection on the attainable SCCI combustion region. Injection timing during the intake process was found to be an important parameter that affects the SCCI region width. We also find it. The effects of mixture stratification and fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• 대한기계학회논문집B
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• 제34권12호
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• pp.1035-1042
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• 2010

HCCI 엔진연소에서 열적성층화 효과는 노킹을 회피하는 수단으로서 생각되고 있다. 본 연구에서는 DME 와 n-Butane 을 연료로 하는 HCCI 엔진연소의 열적성층화 효과를 조사하였다. 예혼합기가 연소실내부에 투입되고 부력의 효과를 이용하여 연소실 내부에 열적성층화를 형성한다. 그 뒤에 피스톤의 압축에 의해서 단열압축 시킨 후 연소실압력과 2 차원화학발광법을 계측하여 해석하였다. 열적성층화가 존재하는 경우에는, 저온산화반응과 고온산화반응의 시작시기가 균질한 경우에 비해서 진각되었고 연소기간은 길어졌다. 발광의 시작은 온도가 높은 곳에서부터 시작하여 온도가 낮은 곳으로 전파 되는 것을 확인하였고 발광기간도 길어짐을 확인하였다.

• 한국자동차공학회논문집
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• 제19권4호
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• pp.64-71
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• 2011

Homogeneous charge compression ignition (HCCI) was the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process was mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. In this paper, detailed kinetic reaction mechanisms of diesel surrogate was investigated to understand the diesel HCCI engine combustion. It was tested two existing mechanisms and two new mechanisms for the comparison of experimental result. The best mechanism for diesel surrogate was suggested through this comparison.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.129-135
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• 2010

Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, $CO_2$ mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.74-79
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• 2005

The Homogeneous Charge Compression Ignition(HCCI) combustion is currently under intensive investigation because of its potential to increase thermal efficiency while greatly decreasing NOx and p.M. In order to account for the thermal boundary layer effects, the two-zone model has been developed to analyze the combustion characteristics of HCCI engine. The detailed chemistry are represented by the GRI mechanism 3.0 involving 53 species and 325reactions. The present combustion model has been validated against the experimental results. Computations are also made for the wide-range operating conditions of HCCI engine.

• 한국전산유체공학회지
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• 제10권2호
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• pp.21-29
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• 2005

In this paper, we present the theoretical and numerical results of scavenge characteristics in a small subchamber of an HCCI(Homogeneous Charge Compression Ignition) engine. Two theoretical models are proposed in prediction of the scavenge time and the efficiency; one is the non-mixing model in which the input gas(CH4) and the existing gas(air) do not mix at all, and the other is the fully-mixed model in which the two gases are assumed to mix completely before ejection. Focus is also given to the effect on the scavenge performance of the size of the chamber outlet.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.75-81
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• 2005

An experimental study on homogeneous charge compression ignition combustion with direct fuel injection was conducted using a single cylinder common-rail diesel engine. To improve the homogeneity of fuel-air mixture, the premixed fuel (gasoline) was injected into premixing chamber and the diesel fuel was injected into the combustion chamber as an ignition source for the gasoline premixture. The experimental results show that soot emissions were dramatically reduced with the increase of fuel premixing ratio, however incomplete products such as HC and CO increased with the increase of the premixed ratio. Earlier injection of Dl diesel fuel increased the IMEP with the decrease of HC and CO concentrations.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.48-54
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• 2004

The purpose of this work is to investigate the effect of premixing condition on the combustion and exhaust emission characteristics in a HCCI diesel engine. To from homogeneous charge before intake manifold, the premixed gasoline fuel is injected into a premixed tank by fuel injection system and the premixed gasoline fuel is ignited by direct injected diesel fuel. Experimental result shows the NOx and soot emissions are decreased linearly with the increase of premixed ratio. In the case of intake air temperature $20^{\circ}C$ with light load, the specific fuel consumptions are increased with the rise of premixed ratio and HC and CO emissions are also increased. But the intake air heating can improve the specific fuel consumption at light load condition because increased air temperature promotes the combustion of premixed mixture. In the case of high intake air temperature with high load condition, premixed fuel is auto-ignited before diesel combustion and soot emission is increased.