• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.90-96
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• 2005

The improvement of combustion stability is very important because it is closely related to the exhaust emission concentrations as well as the fuel consumption during the cold start of SI engine. In our previous studies, the spark and exhaust valve timings were retarded individually from the baseline case to increase the exhaust gas temperature far fast warmup of a close-coupled catalyst. In the study, it was found that combustion stability during cold start becomes worse when the valve timing is retarded from the baseline conditions. The spark and valve timings were simultaneously changed from the baseline conditions to find out the variation of combustion stability during cold start of an Sl engine. Through the study. retarded spark timing by $5^{\circ}$ CA helps improvement of $COV_{imep}$ by $2\%$ and $15^{\circ}C$ increase of exhaust temperature. Retarded exhaust valve timing makes the exhaust gas temperature increase by $30^{\circ}C$, but it also deteriorates the $COV_{imep}$ by $1\%$.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.29-32
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• 2008

Testing was conducted to determine the performance of a residential fuel cell system when subjected to DSS and WSS operation, especially for start-up and shut-down characteristics. In terms of start-up time, it took about 70min to start output power generation and stably to reach 1kW at cold start. Measurement of the characteristics of heat and power generation were carried out at start-up and shut-down time. Fuel gas is used for heating both reformer and stack from start-up to the beginning of power generation. In terms of start-up and shut-down characteristics, it was important to control the reformer temperature precisely. The average output water temperature during the rated output operation(960W) was $63.2^{\circ}C$ constantly. The results of the investigation are being used to develop a new test protocols for residential fuel cell system.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.942-949
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• 2002

The use of a combined starter/generator integrated into the drive train of an automobile offers several possibilities for improvement of fuel economy The use of such a starter/generator system is made feasible by a switch from a 14 volts electrical system to a 42 volts system, however, the sizing of the components is not a trivial problem. This study combines a dynamic electromechanical model of the starter, battery and power electronics with the nonlinear mechanics of the piston/crankshaft system and a thermofluid model of the compression and expansion processes to investigate the cold start problem. The example involves the start of an eight cylinder engine at -25 degrees Celsius. This paper shows how the mechatronic V8 engine of an automotive starter/generator system for the startability works well.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.84-92
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• 2002

On the cold start of LPG engine, as the engine temperature has not reached its equilibrium temperature, liquid LPG could not be changed perfectly gaseous LPG, although it was passed to the vaporizer. Liquid and gas mixed fuel could influence starting ability and exhaust emission characteristics of LPG engine. In this study, the vaporization characteristic of liquid LPG was investigated with a conventional vaporizer and the vaporizer with heat source(glow plug) installed at preheated chamber inlet, by using the visualization methods and engine test. According to visualization result, even if the engine coolant temperature was $14^{\circ}C$, liquid fuel was supplied to primary chamber over 25 seconds without vaporizing from preheated chamber in such a conventional vaporizer. However, the vaporizer with heat source do not correspond with that, scarcely had been trim on glow plug when LPG began to vaporize. The effectiveness of heat source could be verified by application to the conventional LPG engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.51-58
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• 2000

It is well known that the majority of the emissions measured from vehicle exhaust in the US Federal Test Procedure(FTP-75) are emitted during the first 60 seconds. This paper describes an experimental study on SI engine emissions reduction after cold start with interval secondary air injection and coolant control. Secondary air injection after cold start to reduce exhaust emissions causes an exothermic reaction at the exhaust port and gives sufficient air to the catalyst. For that reason engine-out emissions oxidized in the exhaust port and the rapid heating of a catalytic converter after cold start with CSAI and ISAI are estimated. The influence of the coolant temperature on SI engine emissions has been estimated. In the present studycoolant control of the cylinder head tempeature is used to investigate the effect of coolant temperature on SI engine emissions. The results show that engine-out hydrocarbon and carbon monoxide emissions are considerably reduced with interval secondary air injection and coolant control.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.2
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• pp.160-167
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• 1993

As the major methanol fueled vehicle exhaust components, formaldehyde & methanol conversion over the existing commercial 3-way catalyst was examined in a labolatory tains different Ag loadings on commercial 3-way catalyst, and german commercial catalysts for methanol engine exhaust manufactured by a commercial manufacturer. Silver catalysts were prepared by the wet impregnation of silver nitrate solution on commercial 3-way catalyst. These catalysts were characterized with BET Surface area and pore size distribution. In general, the formaldehyde(HCHO) conversion of the tested catalysts was similar to that of methanol$(CH_3OH)$. At 100$^\circ$C, which is equivalent to the cold start condition, 5wt% Ag cat. showed the most excellent HCHO and $CH_3OH$ conversion. The order of activity for conversion of HCHO & $CH_3OH$ to carbon dioxide and water vapor was as follows ; 5wt% Ag/3-way cat.>2wt% Ag/3-way cat.>german cat. front(1) > german cat. rear(2) > 10wt% Ag/3-way cat.> commercial 3-wat catalyst. However there was no significant activity difference between those tested catalysts in the hot run condition of 400$^\circ$C. Therefore, it could be concluded that the Ag-modified 3-way catalyst was the most effective and practical catalyst system which could be capable of removal the HCHO and methanol at the special condition of low temperature such as cold start condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.61-69
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• 2002

To meet stringent LEV and ULEV emission standards, a considerable amount of development work was necessary to ensure suitable efficiency and durability of catalyst systems. The main challenge is to cut off the engine cold-start emissions. It is known that up to 80% of the total hydrocarbons(THC) are exhausted within the first five minutes in case of US FTP 75 cycle. Close-Coupled Catalyst(CCC) provides fast light-off temperature by utilizing the energy in the exhaust gas. However, if some malfunction occurred at engine operation and the catalyst temperature exceeds 1050$\^{C}$, the catalytic converter is deactivated and shows the poor conversion efficiency. This paper presents effEcts of engine operating conditions on catalytic converter temperature in a SI engine, which are the indications of catalytic deactivation. Exhaust gas temperature and catalyst temperature were measured as a function of air/fuel ratio, ignition timing and misfire rates. Additionally, light-off time was measured to investigate the effect of operating conditions. It was found that ignition retard and misfire can result in the deactivation of the catalytic converter, which eventually leads the drastic thermal aging of the converter. Significant reduction in light-off time can be achieved with proper control of ignition retard and misfire, which can reduce cold-start HC emissions as well.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.15-22
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• 2002

As the emission regulations on the automobiles have been increasingly stringent, precise control of air/fuel ration is one of the most important issues on the gasoline engines. Although many researches have been carried out to identify the fuel transport phenomena in the port fuel injection gasolines, mixture preparation in the cylinder has not been fully understood due to the complexity of fuel film behavior, In this paper, the mixture preparation during cold engine start is studied by using a Fast Response Flame ionization Detector.(FRFID) In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient($\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-in. $\alpha$( ratio of directly inducted fuel mass into cylinder from injected fuel mass) and $\beta$ (ratio of indirectly inducted fuel mass into cylinder from wall wetted fuel film on the wall) was increased with increasing cooling water temperature. To reduce a air/fuel ratio fluctuation during cold engine start, the appropriate fuel injection rate was obtained from the wall wetting fuel model. Result of air/fuel ratio control, air/fuel excursion was reduced.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.446-465
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• 2015

In this modern era of technology and information, e-learning approach has become an integral part of teaching and learning using modern technologies. There are different variations or classification of e-learning approaches. One of notable approaches is Personal Learning Environment (PLE). In a PLE system, the contents are presented to the user in a personalized manner (according to the user's needs and wants). The problem arises when a new user enters the system, and due to the lack of information about the new user's needs and wants, the system fails to recommend him/her the personalized e-learning contents accurately. This phenomenon is known as cold-start problem. In order to address this issue, existing researches propose different approaches for recommendation such as preference profile, user ratings and tagging recommendations. In this research paper, the implementation of a novel interaction-based approach is presented. The interaction-based approach improves the recommendation accuracy for the new-user cold-start problem by integrating preferences profile and tagging recommendation and utilizing the interaction among users and system. This research work takes leverage of the interaction of a new user with the PLE system and generates recommendation for the new user, both implicitly and explicitly, thus solving new-user cold-start problem. The result shows the improvement of 31.57% in Precision, 18.29% in Recall and 8.8% in F1-measure.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.363-368
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• 2015

Finding an alternative fuel and reducing environmental pollution are the main goals for future internal combustion engines. The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in a LPG engine. An experimental study was carried out to obtain fundamental data for the emit HC emission characteristics at cold start of pre-mixed LPG and hydrogen in a LPG engine with various fractions of hydrogen-LPG blends. To maintain equal volume ratio of fuel blend, the amount of HC was decreased as hydrogen was gradually added. The results showed that as hydrogen increases, in-cylinder pressure increased. Also emission of unburned hydrocarbon (HC) is sharply decreased.