• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.3
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• pp.297-308
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• 2017

One of the major engine thermal management system(TMS) strategies for improving fuel economy is to operate the engine in high temperatures. Therefore, this work performed a numerical and experimental study to examine the effect of several different STOs(Starting Temperature of Opening) of wax-thermostat, ranging from $85^{\circ}C$ to $105^{\circ}C$, of gasoline engine on fuel economy and emission characteristics. In this study, a gasoline car equipped with waxthermostat was tested and simulated under FTP-75 and HWFET mode. CRUISE $M^{TM}$ was used to simulate vehicle dynamics, transient engine performance and TMS. The test results showed fuel savings for both drive cycles due to higher STO of $100^{\circ}C$, which is slightly worse than that of $90^{\circ}C$ and amounts between 0.34 and 0.475 %. These controversial results are attributed to experimental errors and uncertainty. The computational results for three STOs, $85^{\circ}C$, $95^{\circ}C$ and $105^{\circ}C$, showed that fuel savings attributed to the application of higher STOs of $95^{\circ}C$ and $105^{\circ}C$ are relatively small and range from 0.306 to 0.363 %. It is also found that the amount of HC and CO emissions from the tailpipe tends to decrease with higher engine coolant temperature because of faster catalyst light-off and improved combustion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.137-143
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• 2012

Currently, in order to meet the reinforced emissions regulations for harmful exhaust gas including carbon dioxide ($CO_2$) as a greenhouse gas, technologies for reducing $CO_2$ emission and fuel consumption are being developed. Gasoline direct injection (GDI) systems have the advantage of improved fuel economy and higher power output than port fuel injection gasoline engine systems. The aim of this study is to examine the performance and emission characteristics of a lean burn GDI engine equipped with spray-guided-type combustion system. Stable lean combustion was achieved with a late fuel injection strategy under a constant operating condition. Further improvement in specific fuel consumption is possible with the introduction of multiple fuel injection strategies, which also increases hydrocarbon (HC) and nitrogen oxide ($NO_x$) emissions and decreases carbon monoxide (CO) emission.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.435-441
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• 2010

To verify the possibility of a power generation system using biogas from the waste of pig farm for rural electric production, a SI gasoline engine is modified to use biogas fuel and was installed in a 20 KVA power generation system. An electronic speed regulation unit is developed to keep the system speed at 1500 rpm. Experimental investigations have been carried out to examine the performance characteristics of power generation system (such as: system frequency, phase output voltage,$\ldots$). In addition, the operating parameters and output emissions ($NO_x$, HC, and $CO_2$) of biogas-fueled engine are preliminary evaluated and analyzed for the change of system load. Results indicated that the researched power generation system shows a high stability of output voltage and frequency with help of speed regulator. Biogas fuel (mainly $CH_4$ and $CO_2$) has an environmental impact and potential as a green alternative fuel for SI engine and they would not require significant modification of existing engine hardware. Output emissions of biogas-fueled engine are found to be relative low. $NO_x$ emission increases with the increase of output electric power of the power generation system.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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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.

• Journal of ILASS-Korea
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• v.10 no.1
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• pp.43-52
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI (Port Fuel Injection) gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from 2hole 2spray type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.78-85
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• 2008

The exhaust emission characteristics of a liquefied petroleum gas-di-methyl ether (LPG-DME) compression ignition engine was investigated under homogeneous charge, stratified charge and diffusion combustion conditions. LPG was used as the main fuel and injected into the combustion chamber directly. DME was used as an ignition promoter and injected into the intake port. Different LPG injection timings were tested to verify the combustion characteristics of the LPG-DME compression ignition engine. The combustion was divided into three region which are homogeneous charge, stratified charge, and diffusion combustion region according to the injection timing of LPG. The HC emission was reduced with LPG stratification. However, the carbon monoxide and particulate matter emissions were increased. The ignition timing was advanced with LPG stratification. This advance combustion was because of charge temperature and cetane number stratification with LPG.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.527-534
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• 2006

Modern passenger cars with diesel engines are equipped with DOC(diesel oxidation catalyst) for the purpose of reducing HC and CO in the exhaust stream. Cold start exhaust emissions pose troubles here as on gasoline engine vehicles. As a result, some of the diesel passenger cars roll off todays the assembly lines with WCC(warm-up catalytic converter). Oxidation characteristics of the particulates in WCC is analyzed in this study by EEPS(engine exhaust particulate size spectrometer). The maximum number of PM is found to come out of WCC in sizes near 10nm when an HSDI diesel engine is operated under the conditions of high speed and medium to heavy load. When the temperature of the WCC exceeds $300^{\circ}C$, the number of PM smaller than 30 nm in diameter sharply increases upon passing through the WCC. Total mass of emitted PM gets reduced downstream of the WCC under low speed and light load conditions due to adsorption of PM onto the catalyst. Under conditions of high speed and medium to heavy load, the relatively large PM shrink or break into fine particles during oxidation process within the WCC, which results in more mass fraction of fine particles downstream of the WCC.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.1-6
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• 2003

Engine emission regulations are becoming more stringent nowadays. In cold transient regime, about 80% THC is exhausted to the atmosphere in the first 200s (US FTP cycles). Accordingly, reducing emission levels in the cold period immediately after the engine start before the catalysts reach their working temperature will be an especially critical factor in meeting more stringent regulations in the future. In this study, the total hydrocarbon quantities are measured using a Fast FID with gasoline fuel for a 4-cylinde. Sl engine, including Secondary Air Injection (SAI) system. Commercial SAI device's direction is reverse to the exhaust flow. In this study, a swirl flow type SAI system which is positioned between the exhaust manifold and exhaust port, was developed. We compared the swirl type secondary air injection with a commercial secondary air injection of .everse flow. The swirl type SAI showed better results in reducing HC by 26% than the commercial flow type SAI of reverse flow which was caused by the better mixing between the exhaust gas and the secondary air.

• Journal of the Korean Society of Combustion
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• v.16 no.3
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• pp.52-58
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• 2011

The purpose of this paper is to investigate the effect of equivalence ratio on the combustion and emission characteristics of a compression ignition engine fueled with biodiesel. In this research, a single-cylinder direct injection engine with 373.3 cc of displacement volume was tested on DC dynamometer. In order to investigate the effect of biodiesel equivalence ratio on combustion characteristics, the experiments were conducted at various equivalence ratios and injection pressures of 40~120 MPa. For investigating engine performance, lambda meter was connected and equivalence ratios was varied from 0.6 to 1.0. In addition, the exhaust emissions such as oxides of nitrogen($NO_X$), hydrocarbon(HC) and carbon monoxide(CO) were measured by exhaust gas analyzer under the various air/fuel ratios. The experimental results show that maximum IMEP was measured at the 0.8 of equivalence ratio. Furthermore, $NO_X$ emission was rapidly decreased as the increase of equivalence ratio. However soot emission was significantly increased according to the increase of equivalence ratio.