• Fire Science and Engineering
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• v.18 no.2
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• pp.34-40
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• 2004

The effects of external flow excitation with various frequencies and amplitudes on the flame behavior and pollution emission characteristics from a laminar jet flame are experimentally investigated. Measurements of $NO_x$ emission indices ($EINO_x$), performed in vertical lifted flame like turbulent with various exciting amplitude at a constant resonance frequency, have been conducted. It was also conducted to investigate the effects of excited frequency at a constant exciting amplitude on $NO_x$ emissions with a various frequency ranged 0 Hz to 2 KHz. From the vertical lifted turbulent flame of the excited jet with resonance frequency by strong excitation was shown that the dependence of $NO_x$ emission could be categorized into three groups Group I of long flame length with high disturbances yielding high $NO_x$ emission, Group II of intermediate flame length and relative narrow flame volume with low disturbance yielding low $NO_x$ emission and Group III of long flame length and large flame volume with high time ＆ space disturbances behaviour yielding high $NO_x$ emission.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.629-636
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• 2022

Domestic eco-friendly vehicles currently account for 5.8% of the total registered vehicles in Korea. Hydrogen vehicles, one of the representative eco-friendly vehicles, have grown rapidly as they have been expanded to the market based on the government's policy to boost the hydrogen industry. Therefore, it is time to expand the safety review of hydrogen vehicles in various directions according to the increase in supply. In this study, the effect of internal heat damage was analyzed when a jet flame was generated by a hydrogen car in a road tunnel. It was simulated using Fluent, and the amount of jet flame injection was selected in consideration of the hydrogen tank capacity of commercial hydrogen vehicles for road tunnels. In addition, the study was conducted with the direction of the jet flame and the nozzle distance from the tunnel wall as variables. From the results, when the jet flame erupted in the road tunnel, high radiant heat emission of more than 20 kW/m² was generated in most areas within ±5 m in the longitudinal direction based on the vehicle (spray nozzle) and 5 to 7 m in the lateral direction based on the adjacent tunnel wall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.275-282
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• 2010

The effect of swirl flow on NOx in a nonpremixed turbulent hydrogen jet with coaxial air was studied. The swirl vane angle was varied from $30^{\circ}$ to $90^{\circ}$. The fuel jet air velocity and coaxial air velocity were varied in an attached flame region as $u_F=85{\sim}160m/s$ and $u_A=7{\sim}14m/s$. The objective of the current study was to analyze the characteristics of nitrous oxide emission in a swirl flow and to propose a new parameter for EINOx scaling. The experimental results show that EINOx decreases with the swirl vane angle and increased with flame length. Further, EINOx scaling factors can be determined by considering the effective diameter ($d_{F,eff}$) in a far field concept. The EINOx increased in proportion to the flame residence time (${\sim}{\tau_R}^{1/2.8}$) and the global strain rate (${\sim}{S_G}^{1/2.8}$).

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.1-9
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• 1999

The NOx production and combustion characteristics are experimentally compared with an offset with counter-orifice configuration. The offset-opposed impinging flame creates stronger vortex around the stagnation point than the opposed flame. The thermal and mass mixtures be improved and the delay of turbulence dissipation be occurred by the strong vortex. In result, the turbulent flame structure transferred from the wrinkled flame and the corrugated flame to the distributed reaction flame. It was found that the offset-opposed impinging flame decreased more NOx and improved the combustion efficiency than the opposed flame. The principal objective of this study is to develop the low NOx combustor by distributed reaction flame.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.431-438
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• 2011

Flame lift-off conditions determine the operating conditions of burners. It is known that a flame can be lifted when the Schmidt number (Sc), which is the ratio of the dynamic viscosity to the mass diffusivity, is greater than unity. In this study, the flame lift-off characteristics of non-premixed flames of propane (Sc > 1) and methane (Sc < 1) in a coaxial outer air tube were experimentally compared. The experimental results indicated that stable lifted flames could be obtained even when Sc < 1 in a confined air tube. On the basis of the results of a simple numerical analysis, it was confirmed that a new flame stabilization mechanism exists in the tube. A velocity field is preferentially developed upstream of the flame, and it results in a new stabilization condition. This result can be very useful in explaining the stabilization of the flames of ordinary burners in which a flame is produced in a confined space.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.23-27
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• 2014

The use of electromagnetic energy and non-equilibrium plasma for enhancing ignition and combustion stability is receiving increased attention recently. The conventional technologies have adapted the electrical devices to make the electromagnetic field, which resulted in various safety issues such as high-maintenance, additional high-cost system, electric shock and explosion. Therefore, an electrodeless microwave technology has an advantage for economic and reliability compared with conventional one because of no oxidation. However, the application of microwave has been still limited because of lack of interaction mechanism between flame and microwave. In this study, an experiment was performed with jet diffusion flames induced by microwaves to clarify the effect of microwave on the combustion stability and pollutant emissions. The results show that microwave induced flames enhanced the flame stability and blowout limit because of abundance of radical pool. However, NOx emission was increased monotonically with microwave intensity except 0.2 kW, and soot emission was reduced at the post flame region.

• 전기의세계
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• v.24 no.1
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• pp.75-85
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• 1975

In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.74-80
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• 2019

Hydrogen refueling stations that use compressed hydrogen at high pressure provide safety distances between facilities in order to ensure safety. Most accidents occurring in hydrogen stations are accidental leaks. When a leak occurs, various types of ignition sources generate a jet flame. Therefore, the analysis of leaked gas diffusion and jet flame due to high pressure hydrogen leakage is one of the most important factor for setting the safety distance. In this study, the leakage accidents that occur in the hydrogen refueling station operated in high pressure environment are simulated for various leakage source sizes. The results of this study will be used as a reference for the future safety standards.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.158-165
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• 2022

Eco-friendly policies proposed by the government of The Republic of Korea have encouraged the use of eco-friendly vehicles. Hydrogen vehicles have exhibited the highest growth rate, although the current number of registered vehicles is low. In hydrogen vehicles, a thermally activated pressure relief device (TPRD) is installed to prevent explosions in the hydrogen gas cylinder. When discharged due to low ignition energy, hydrogen gas readily forms a jet flame. The risks induced by such jet flames were analyzed through a numerical analysis. Jet flames can activate TPRDs installed in nearby hydrogen gas cylinders. As a result, high-voltage cables exposed in the lower area of a vehicle can ignite within seconds. There was a 9.5-kW/m2 area around the vehicle (which can result in casualties) at a distance of ~5 m from the hydrogen gas cylinder, and a 37.5-kW/m2 area (which can cause significant damage) in the form of an inverted triangle toward the lower section of the vehicle. We believe that the risk factors analyzed herein should be considered for addressing accidents in hydrogen vehicles.

• Fire Protection Technology
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• s.21
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• pp.5-12
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• 1996

An experimental investigation has been made with the objcetive of studying the effects of air entrainment of fire strength. A rich jet flame is considered as an fire, and fire, and the air entrainment is controlled by introducing the tone excitation which is generated by means of a loudspeaker-driven cavity. The excitation frequency is chosen for the resonant frequency identified as a pipe resonance due to acoustic excitation. As the excitation intensity increases, the amplitude of oscillating velocity for inducing air entrainment is increased, the flame height decreased and the structure of diffusion flame gradually transformed to that of premixed flame.