• Journal of the Korean Society of Combustion
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• v.18 no.2
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• pp.1-7
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• 2013

Flame stabilization characteristics of premixed flames in narrow annular coaxial tubes (NACT) were investigated experimentally. The NACT burner was proposed as a model of a cylindrical refractory burner, and it was made of quartz tubes. Flame stabilization conditions affected by the characteristic length of the burner was investigated with the variation of the equivalence ratio and the flow rates. Flame behaviors in narrow spaces could be directly observed. Conclusively, more wide flame stabilization conditions could be obtained at the case of the decreased channel scale. A flame instability, such as combustion noise was detected concerned with the flame oscillation observed at the surface of multi channel stage. Some flame propagation characteristics had complicated tendencies that may exist in practical porous-media combustors. Therefore, this NACT burner can be a basic configuration for the development of flame stabilization model in porous media combustor, and it will enhance our understanding about the behavior of flames in meso-scale combustion spaces.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1582-1590
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• 1998

Combustion-driven oscillations in a surface burner have been investigated to clarify their characteristics. A model combustor is made and the oscillation frequencies are measured for various dimensions of the combustor. It is found that there are two modes of oscillations; one is the 'acoustic mode' at high frequencies, associated with the acoustic mode of the combustion system and the other is the 'combustion mode' at low frequencies around 100 Hz, associated with the instability of the flame. Acoustic mode is excited when the surface burner is placed where the phase of particle velocity leads that of acoustic pressure by $90^{\circ}$, for all the combustion conditions. Combustion mode is driven at high combustion rate by the lift of unstable flame near the lower limit of the combustible equivalence ratio. Combustion mode is greatly influenced by the inlet temperature of the premixed gas. When the inlet temperature is very high, the combustion mode does not occur.

• Journal of the Korea Safety Management & Science
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• v.5 no.1
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• pp.115-128
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• 2003

To comparison the surface treatment methods of stone board materials, the results of Dorry's abrasive test were 23.4 for water-jet system and 18.9 for flame-burner system. Therefore abrasive hardness, the stone board materials by the water-jet system was greater than one by flame-jet system. As a result of Shore's hardness test, the stone board materials by water-jet system was twice greater than one by flame-jet system. Authors carried out microscopic observation to survey a defection of the composition minerals for two methods, but all of the both methods have not founded a defection. Therefore, the stone board materials by water-jet system was greater durability than one by flame-jet for the surface treatment methods.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2154-2159
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• 2007

The potential of using a double-faced wall stagnation flow burner in mass production of carbon nanotubes was evaluated experimentally and computationally. With nitrogen-diluted premixed ethylene-air flames established on the Nickel-coated stainless steel double-faced wall, the propensities of carbon nanotube formation were experimentally determined using SEM and FE-TEM images and Raman spectroscopy, while the flame structure was computationally predicted using a 3-dimensional CFD code with a reduced reaction mechanism. The uniformity and yields of synthesized carbon nanotubes were evaluated in terms of the flame stretch rates. Results show substantial increase of area on the wall surface where uniform carbon nanotubes are synthesized with using the double-faced wall stagnation flow burner due to enhanced uniformity of temperature distribution along the wall surface and support the potential of using a double-faced wall stagnation flow burner in mass production of carbon nanotubes.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.49-53
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• 2001

A conventional flame type gas combustion major portion of heat is transferred to the body by convection due to small radiant ability of the gas flame. Increasing the radiation component of heat flux in the combustion zone allows to augment the efficiency of gas utilization. Such effect can be reached by using radiative gas burner applied to metal mesh combustion. Basically the gas radiant burner consists of metallic mesh of high heat resisting steels. In terms of this regards, we have made the burner consisted of metal mesh and measured the radiative flame stability of natural gas/air mixture on the metal mesh burner. The pressure loss through the metal mesh is defined by pressure-velocity slope. The more increased the pressure-velocity slope of the metal mesh is, the wider the stable zone of radiave flame on the metal mesh burner is. And the augmentation of mixture flowrate through the metal mesh make narrow the permissible range of equivalence ratio.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.254-255
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• 2005

The effect of surrounding air velocity on the soot deposition process from a diffusion flame to a solid wall was investigated in a microgravity environment to attain in-situ observations of the process. An ethylene($C_2H_4$) diffusion flame was formed around a cylindrical rod burner in surrounding air velocity of $v_{air}$=2.5, 5, and 10 cm/s with oxygen concentration of 35 % and wall temperature of 300 K. Laser extinction was adopted to determine the soot volume fraction distribution between the flame and burner wall. The experimental results show that the soot particle distribution region moves closer to the surface of the wall with increasing surrounding air velocity. A numerical simulation was also performed to understand the motion of soot particles in the flame and the characteristics of the soot deposition to the wall. The results successfully predicted the differences in the motion of soot particles by different surrounding air velocity near the burner surface and are in good agreement with observed soot behavior in microgravity. A comparison of the calculations and experimental results led to the conclusion that a consideration of the thermophoretic effect is essential to understand the soot deposition on walls.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.512-522
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• 2018

This study was conducted to investigate on the combustion characteristic with the effects of mat thickness and fuel kinds in a metal-fiber burner. The mode transition point is confirmed by the K value, which was defined as the rate of flow velocity and laminar burning velocity. The ($T^4_{sur}-T^4_{\infty}$) is highest at methane flame with 3 T thickness. Through the measurement of the unburned mixture temperature, the possibility of submerged flame in surface combustion burner was confirmed. The rapid emission of CO occurs nearby limit blow out (LBO) because of the increase of flow velocity. In case of NOx, the trend is similar with surface temperature. However, it also considered that the NOx emission is affected by residence time with flame position.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.197-204
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• 2013

A method was developed for analyzing the radiation heat transfer from the duct burner flame to the heat exchanger in a heat recovery steam generator (HRSG) in order to supplement the existing thermal design process. The burner flame and the heat exchanger were considered to be imaginary planes, and the flame temperature, surface, and emissivity were simplified using an engineering approach. Three analysis cases in which the duct burner position and fuel were changed were considered. The calculated flame radiative heat transfer and local flux on the heating surface were compared with those of 3-atomic gas radiation and convection. In all analysis cases, heat transfer by 3-atomic gas radiation was very small. The ratio of the flame radiative heat transfer to the convection heat transfer on the heating surface was estimated to be as high as 8-41%. Moreover, the local heat flux on the heating surface centerline was dominated by flame radiative heat flux.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.96-104
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• 2006

In the present paper, the effects of combustion instability on flow structure and flame dynamic with the configurations of burner exit in a model gas turbine combustor are investigated using large eddy simulation(LES). A G-equation flamelet model is employed to simulate the unsteady flame behavior. As a result of mean flow field, the change of divergent half angle(${\alpha}$) at burner exit results in variations in the size and shape of the central toroidal recirculation(CTRZ) as well as flame length by changing corner recirculation zone(CRZ). The case of ${\alpha}=45^{\circ}$ show smaller size and upstream location of CTRZ than that of $90^{\circ}$ and $30^{\circ}$ by the development of higher swirl velocity. The flame length in the case of ${\alpha}=45^{\circ}$ is the most shortest, while that in the case of ${\alpha}=30^{\circ}$ is the longest by the decrease of effective reactive area with the absence of CRZ. Through the analysis of pressure fluctuation, it is identified that the case of ${\alpha}=45^{\circ}$ shows the most largest damping effect of pressure oscillation in all configurations and brings in the noise reduction of 2.97dB, comparing with that of ${\alpha}=30^{\circ}$ having the largest pressure oscillation. These reasons are discussed in detail through the analysis of unsteady phenomena about recirculation zone and flame surface. Finally the effects of flame-acoustic interaction are evaluated using local Rayleigh parameter.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.37-41
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• 2004

Quenching phenomena is one of major concern in development of millimeter or sub-millimeter scale micro combustor for the size of the combustor is near extinction condition. In this work we focused on the effect of combustor wall condition that was parameterized by Perovskite LSC($La_{0.8}$$Sr_{0.2}$$CoO_3$) redox catalyst. The experiment was done by variable gap-width 2D wall equipment. The flame was produced by premixed methane-air jet issuing from millimeter-scale slot burner and it propagated through the narrow gap of the walls. By comparison of flame behaviour near catalyst-coated wall and simple glass wall, we investigated the effect of possible surface reaction on quenching phenomena. The flame between two plates was observed where the gap of the plates was reduced stepwise from 20mm to a distance of quenching occurrence. The two flames with and without surface modification were almost same by observation. But the gap for the occurrence of quenching was increased between catalyst-coated wall. So we concluded that surface reaction close to combustor wall has a negative effect on micro combustion.