• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• Journal of ILASS-Korea
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• v.10 no.2
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• pp.41-47
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And. it is extremely difficult to increase gasoline engine efficiency and to reduce NOx and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper. internal EGR(exhaust gas recirculation) effect is suggested to realize CAI combustion. An experimental study was carried out to achieve CAI combustion using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). A flame trap was used to simulate internal EGR effect and to increase flame propagation speed in the CVCC. Flame propagation photos and pressure signals were acquired to verify internal EGR effect. Flame trap creates high speed burned gas jet. It achieves higher flame propagation speed due to the effect of geometry and burned gas jet.

• Fire Science and Engineering
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• v.29 no.3
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• pp.31-36
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• 2015

This study analyzed the flame characteristics when igniting 200 ml of flammable liquids containing equal parts gasoline and another flammable liquid. These mixtures were used to fill a divided space in a simulation. The length of one side of the divided space was 2,000 mm, and the length of the combustion device was 1,000 mm. The mixture with alcohol had the highest flame propagation speed (0.7 s), while the mixture with light oil showed the lowest (1.2 s). The gasoline and acetone mixture reached peak flame in 25.5 s, at the highest speed, while the mixture with light oil reached peak flame in 163.7 s at the lowest speed. The gasoline and light oil showed the longest continuous combustion time (332.7 s), while the gasoline and paint thinner showed the shortest (121.5 s). A fire inspector who is examining the scene of a fire needs to analyze both the statements of the first eyewitness and the flame characteristics collectively.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1749-1757
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• 2019

Predicting lower flammability limits (LFL) of hydrogen has become an ever-important task for safety of nuclear industry. While numerous experimental studies have been conducted, LFL results applicable for the harsh environment are still lack of information. Our aim is to develop a calculated non-adiabatic flame temperature (CNAFT) model to better predict LFL of hydrogen mixtures in nuclear power plant. The developed model is unique for incorporating radiative heat loss during flame propagation using the CNAFT coefficient derived through previous studies of flame propagation. Our new model is more consistent with the experimental results for various mixtures compared to the previous model, which relied on calculated adiabatic flame temperature (CAFT) to predict the LFL without any consideration of heat loss. Limitation of the previous model could be explained clearly based on the CNAFT coefficient magnitude. The prediction accuracy for hydrogen mixtures at elevated initial temperatures and high helium content was improved substantially. The model reliability was confirmed for $H_2-air$ mixtures up to $300^{\circ}C$ and $H_2-air-He$ mixtures up to 50 vol % helium concentration. Therefore, the CNAFT model developed based on radiation heat loss is expected as the practical method for predicting LFL in hydrogen risk analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.358-370
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• 1997

In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.659-669
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• 1996

To clarify the effects of equivalence ratio, initial pressure and temperature on the flame propagation and radicals characteristics, a series of the experimental study were conducted in a quiescent methane-air premixture using a constant volume chamber. The development of the flame was visualized following the start of ignition using high speed schlieren photo and radical images by intensified CCD camera. Combustion pressure and ion current were recorded simultaneously according to the experimental conditions which were equivalence ratio with 0.7 to 1.2, initial pressure with 0.08 MPa to 0.40 MPa and initial premixture temperature with 3l3.2K to 403.2K. The results showed that the flame speed by ion current and mass fraction burned by combustion pressure characterized the effects of flame propagation very well. And increased combustion duration due to lean combustion condition that was below equivalence ratio, 0.8 caused cycle variation and decreasing the power of engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.44-51
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• 2017

An experimental results on the dynamic characteristics of hydrocarbon/air premixed flames with ultrasonic standing waves are presented and compared. Images of the propagating flames were acquired by using a high-speed camera, and the flame behavior of methane/air and propane/air premixed flame were closely scrutinized through the image post-processing. At the fuel-lean conditions, the flame propagation velocity increased due to the intervention of the ultrasonic standing wave and vice versa at the fuel-rich conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.156-167
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• 1996

The present work is a continuation of our previous study to investigate the effects of parameters such as equivalence ratio, hydrogen supplement rate and initial pressure on combustion characteristics in a disk-shaped constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The flames in near stoichiometric mixture of methane-air are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed to an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate. Also, flame is sluggishly propagated at increased initial pressure in combustion chamber. Volume fraction of burned gas and flame radius as the combustion characteristics are increased by increasing the hydrogen supplement rate, especially at the combustion middle period, but then are slowly increased by increasing the initial pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.30-40
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• 1995

Optically accessible D. I. diesel engine with a rectangular combustion chamber was constructed to visualize the behaviors of sprays and flames in the combustion camber with the close conditions of pressure and temperature in an actual engine. The behaviors of sprays and flames in the combustion chamber as the operating conditions of this engine were photographed with high speed camera by Diffused Background Illumination Method. With photographs taken by this method, behavior of spray droplets injected into the combustion chamber, ignition points, and flame propagation were observed and analyzed at a time-and space-dependent fashion.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.572-579
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• 2009

This study is to investigate experimentally the flame structure and propagation mechanism in dust explosions and to provide the fundamental knowledge. Upward propagating laminar dust flames in a vertical duct of 1.8 m height and 0.15 m square cross-section are observed and flame front is visualized using by a high-speed video camera. Also, the thicknesses of preheated and reaction zone have been determined by a schlieren, electrostatic probe and thermocouple. The thickness of preheated zone in lycopodium dust flame is observed to be 4~13 mm, about several orders of magnitude higher than that of premixed gaseous flames. From the experimental results by a PIV(Particle Image Velocimetry) system, a certain residence time of the unburned particle in preheated zone is needed to generate combustible gas from the particle. The residence time will depend on preheated zone thickness, particle velocity and flame propagation velocity.