• 한국자동차공학회논문집
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• 제5권6호
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• pp.183-191
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• 1997

For the improvement of ignitability we need ignition energy and its discharge characteristics which are suitable for a part distribution of the mixture density around the ignition spark plug and the flow characteristics of the mixture in the combustion. Especially, for the solving of the instability of initial ignition and lean ignitability limit in the case of lean-burn combustion, the more powerful ignition energy is required. The conclusions from the observation can be summarized as follows: 1) The ignitability limit for HIS expands wider and the combustion is more stable than for CDI. 2) The combustion duration and ignition timing depend upon the distribution of local mixture density in the vicinity of ignition spark plug.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.37-44
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• 1998

Lean burn combustion is an important concept for improving the fuel consumption and exhaust emissions. However, the lean burning is associated with increased cycle-to-cycle combustion variations due to the ignition instabilities and redu- ced flame propagation rates. Engine stability under lean mixture conditions could be improved by increasing flame speed through enhanced flow characteristics and by securing ignitability with improvement of ignition systems. The effects of flow motion and ignition characteristics on the combustion performances were investigated in a 4-valve SI engine. Flow motions of tumble-swirl were varied with a swirl control valve attached at the inlet ports, while ignition energy and its distribution were controlled in a high -frequency ignition system by changing spark duration and spark frequency. The improvement of lean burn performance by the optimum flow motion and ignition characteristics is discussed.

• 에너지공학
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• 제24권3호
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• pp.61-66
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• 2015

Homogeneous charge compression ignition (HCCI) engine combines the combustion characteristics of a compression ignition engine and a spark ignition engine. HCCI engines take advantage of the high compression ratio and heat release rate and thus exhibit high efficiency found in compression ignition engines. In modern research, simulation has be come a powerful tool as it saves time and also economical when compared to experimental study. Engine simulation has been developed to predict the performance of a homogeneous charge compression ignition engine. The effects of compression ratio, cylinder pressure, rate of pressure rise, flame temperature, rate of heat release, and mass fraction burned were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion characteristics model for a homogeneous charge compression ignition engine running with isooctane as a fuel and effect of compression ratio.

• 한국안전학회지
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• 제36권3호
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• pp.1-6
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• 2021

Hydrogen is considered a cleaner energy source than fossil fuels. As a result, the use of hydrogen in daily life and economic industries is expected to increase. However, the use of hydrogen energy is currently limited because of safety issues. The rate of combustion of the hydrogen mixture is about seven times higher than that of hydrocarbon fuels. The hydrogen mixture is highly flammable and has a low minimum ignition energy. Therefore, it presents considerable risks for fire and explosions in all areas of hydrogen manufacturing, transportation, storage, and use. In this study, the auto-ignition characteristics of hydrogen were investigated numerically for diluted hydrogen mixtures. Auto-ignition temperature, a critical property predicting the fire and explosion risk in hydrogen combustion, was determined in well-stirred reactors. When N₂ and CO₂ were used to dilute the hydrogen/air mixture, the ignition delay time increased with increasing dilution ratios in both cases. The CO₂-diluted mixtures exhibited a longer ignition delay than the N₂-diluted mixtures. We also confirmed that lower initial ignition temperatures increased the ignition delay times at 950 K and above. Overall, the auto-ignition characteristics, such as the concentrations of participating species and ignition delay times, were primarily affected by the initial temperature of the mixture.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.75-82
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• 2004

The allowable exhaust standard has been intensified as a part of the countermeasure to decrease air pollution in the world. As the cars with an alternative fuel starts to get into the spotlight, the cars with low emission has been introduced and exhaust gas regulation forced in this country. These days, LPG vehicles, which infrastructure of fuel was already built up, and CNG vehicles are recognized for alternative fuel cars in this country. In this study, the constant volume combustion chamber was manufactured and used for experiments to obtain the ignition characteristics of LPG fuel and the optimal ignition energy. The experiment measured the combustion characteristics, in regard to the change of combustion variable, and the change of ignition energy. During the combustion of fuel, the maximum temperature inside the combustion chamber is higher when the initial pressure is higher. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux did not change much with the theoretical correct mixture but the various initial temperature of the combustion chamber. The heat flux got faster and ignition energy bigger as the dwell time of the ignition system expanded. When the dwell time get longer, the ignition energy also increased then fixed. The ignition energy increased as the initial pressure inside the combustion chamber higher. The heat flux got faster as the dwell time expanded.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.47-55
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• 1998

A new ignition system concept was developed to improve ignition performance, accuracy of control and the reliability of the ignition system. The new ignition system has ho호 frequency discharge characteristics with 1.5-2.0 ms discharge duration, in place of the usual solitary longer duration event. We applied the system to a commercial engine to study its influence on the maximum combustion pressure attained during the cycle, when this peak pressure occurred, imep, variation rate of the engine speed and the flammability limit of a lean mixture. In this study, we clarified that the new ignition system had a beneficial effect of the lean mixture flammability limit. Also for a given mixture strength we found that the mew ignition system gave a higher peak cylinder pressure than in the case of the conventional ignition system.

• 동력기계공학회지
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• 제20권2호
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• pp.32-42
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• 2016

Under part load condition of spark-ignition engine, pumping loss had great effect on engine efficiency. To reduce pumping loss, the study designed spark-ignited engines to make direct spray of gasoline to combustion chamber. In spark-ignited direct-injection engines, ignition probability is important for successful combustion and flame propagation characteristics are also different from pre-mixed combustion. This study designed a visualization testing device to study ignition probability of spark-ignited direct-injection LPG fuel and combustion flame characteristics. This visualization device consists of combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. Ambient pressure, ambient temperature and ambient air flow velocity are important parameters on ignition probability of LPG-air mixture and flame propagation characteristics, and the study also found that sprayed LPG fuel can be directly ignited by spark-plug under proper ambient conditions. To all successful cases of ignition, the study recorded flame propagation image in digital method through ICCD camera and its flame propagation characteristics were analyzed.

• 펄프종이기술
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• 제34권2호
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• pp.42-46
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• 2002

Wallpaper has been used for decorating wall with multifarious patterns and colors. Ignition characteristic of wallpapers depends upon the types of wallpapers and their components. Since the wallpaper is made of flammable cellulose fibers diverse materials are being used as flame retardant in producing wallpapers. In this paper the ignition characteristics wallpapers prepared with three different fillers and pretreated polyester fibers were examined. Also the effect of calendering on ignition characteristics was investigated. Commercial papers were used for checking the effect of calendering on the ignition characteristics of treated paper In this experiments, guanidine sulfomate was used as flame retardant.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.551-559
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• 1998

Evaporation and ignition characteristics of fuel droplet have major influences on the efficiency and performance of engine. In the present study the experiment of evaporation and self-ignition of single fuel was performed under the various ambient conditions. An individually suspended droplet of n-heptane n-hexadecane ethyl-alcohol and light oil were employed as a liquid droplet. Evaporation and ignition characteristics were measured by using the video-camera and image processing technique under the various ambient temperatures (up to 1000310 OC)and partial pressure of oxigen(up to 60%) The evaporation curve shows that the droplet life time ignition delay time decreases as the ambient temperature and partial pressure of oxigen increase, The temperature variations of droplet were also reported for various fuel and ambient temperatures. The numerical simulations were carried out to predict droplet diameter and temperature with favorable agreement.

• 한국안전학회지
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• 제16권1호
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• pp.48-52
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• 2001

This study was undertaken to investigate fire risk characteristics of the plastics foam that is used an insulating materials in workplaces. The ignition characteristics and combustion gas of the plastics foam were carried out using the ISO self-Ignition tester, the Cone Calorimeter, and NES combustion analyzer. The experimental materials used were commercial samples and their composition is not disclosed by the manufacturer. As the experimental results, the self-ignition temperature of the plastics foam ranges from $410^{\circ}C$ to $510^{\circ}C$, and the flash-ignition temperature of plastics foam ranges from $370^{\circ}C$ to $450^{\circ}C$. The difference of ignition temperature on density with plastics foam type was smaller since the amount of combustible gas to ignite is not caused enough. The time to ignition of the polyethylene foam in samples of the plastics foam was shorter, and its of polyethylene foam was longer. The concentration of carbon dioxide of the polyethylene foam shows higher in samples of the plastics foam. It is found that the concentration values of carbon monoxide of the plastics foam show very fatality on people during exposure of 30 minutes in fire.