• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.10-18
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• 2004

It is well known that the stratified charge combustion has many kind of advantages to combustion characteristics, such as higher thermal efficiency and less CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can be caused low fuel consumption, it is produced the high unburned hydrocarbon and soot levels because of different equivalence ratio in the combustion chamber. Moreover it has a lot of possibility of low output and misfire if the mixture gas would not be in existence around the spark plug. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The effect of locally mixture gas distribution according to control the direct injection and premixed injection in the chamber were examined experimentally. In addition, the effects of turbulence on stratified charge combustion process were observed by schlieren photography.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.37-40
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• 2013

Hydrogen-dimethy ether (DME) and hydrogen-diesel compression ignition engine combustion were investigated and compared each other in a single cylinder compression ignition engine. Hydrogen and DME were used as low carbon alternative fuels to reduce green house gases and pollutant. Hydrogen was injected at the intake manifold with an injection pressure of 0.5 MPa at fixed injection timing, $-210^{\circ}CA$ aTDC. DME and diesel were injected directly into the cylinder through the common-rail injection system at injection pressure of 30 MPa. DME and diesel inejction timing was varied to find the optimum CI combustion to reduce CO, HC and NOx emissions. When DME was injected early, CO and HC emissions were high while NOx emission was low. Fuel consumption, heat release rate, and exhaust emissions were measured to analyze each combustion characteristics of each ignition promoter. Fuel consumption was decreased when diesel was used as an ignition promoter. This is due to the lower volatility of diesel which created more stratified charge than DME.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.153-156
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• 2012

Direct numerical simulations (DNSs) of ignition of lean primary reference fuel (PRF)/air mixtures under homogeneous charge compression ignition (HCCI) conditions are performed using 116-species reduced chemistry. The influence of variations in the initial temperature field, imposed by changing the variance of temperature, and the fuel composition on ignition of lean PRF/air mixtures is studied using the displacement speed analysis.

• Journal of Photoscience
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• v.4 no.2
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• pp.53-59
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• 1997

Absorption and fluorescence studies of E-1-(p-methoxyphenyl)-2-(p-nitrophenyl) ethene in homogeneous solvents, polymer matrix and normal and reverse micelles showing strong solvatochromic fluorescent emission properties with quasi-planar intramolecular charge transfer characteristics in the electronically excited singlet state are discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.49-54
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• 2003

The purpose of this work is to investigate the effect of premixed fuel on the reduction of exhaust emissions in premixed charge compression ignition engine. The premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber. The pre-mixture is ignited by a small amount of diesel fuel directly injected into the cylinder. In the case of gasoline as a premixed fuel of the engine, $NO_x$ and smoke concentration of exhaust emissions were reduced compared with the conventional diesel engine. But in the event of diesel fuel for premixed fuel, the rate of smoke reduction was small compared with the case of gasoline as a premixed fuel. HC and CO emissions were increased at high premixed ratio in the case of two premixed fuels. The combustion characteristics of the engine such as the combustion pressure, the rate of heat release, and other characteristics are compared.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.25-31
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• 2006

Controlled Auto Ignition(CAI) combustion has great potential in achieving significant increase in engine efficiency, while simultaneously reducing exhaust emissions. The process itself involves the auto ignition and subsequent simultaneous combustion of a premixed charge. In this study, NVO(Negative Valve Overlap) system was applied to a CAI engine in order to use residual gas. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port to initiate CAI combustion. This paper introduced the valve timing strategy and experimental set-up. From this study, the effect of engine speed and valve timing on CAI combustion and exhaust emissions was clarified. In addition, stratified charge method was used to extend CAI operating region.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.182-189
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• 2005

In order to investigate the effect of premixed gasoline, diesel fuel, and n-heptane charges on the combustion and exhaust emission characteristics in a direct injection (DI) diesel engine, the experimental studies are performed. The premixed fuels are injected into the premixing chamber that installed upstream of the intake port in order to minimize the inhomogeneity effect of premixed charge. The injection nozzle for directly injected fuel is equipped in the center of the combustion chamber. The air temperature control system is equipped in the intake manifold to examine the effect of air temperature. The experimental results of this study show premixing fuel is effective method to reduce the NOx and soot emissions of diesel engine. NOx emissions are linearly decreased with increasing premixed ratio for the three kinds of premixed fuels. The heating of intake air $(80^{\circ}C)$ reduced the deterioration of BSFC in high premixed ratio, because it promotes evaporation of premixed diesel droplet in the premixing chamber.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1035-1042
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• 2010

The thermal stratification effect has been thought as one of the way to avoid dramatically generating the heat from HCCI combustion. We investigate the effect of thermal stratification on HCCI combustion fueled by DME and n-Butane. The thermal stratification occurs in a combustion chamber of a rapid compression machine with premixture by buoyancy effect that is made of fuel and air. The premixture is then adiabatically compressed, and during the process, the in-cylinder gas pressure is measured and two-dimensional chemiluminescence images are prepared and analyzed. Under the thermal stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous case. Further, the LTR period and the luminosity duration under homogeneous conditions are shorter than the corresponding quantities under stratified conditions. Additionally, under stratified conditions, the brightest luminosity intensity is delayed longer than that of homogeneous condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.75-82
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• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.