• Title/Summary/Keyword: 대향류 확산화염

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Effect of Fuel Mixing on PAH and Soot Formation in Counterflow Diffusion Flames (다양한 연료의 혼합에 따른 대향류 확산화염에서의 PAH 및 매연생성 특성)

  • Yoon, S.S.;Lee, S.M.;Chung, S.H.
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.137-142
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    • 2003
  • In order to investigate the effect of fuel mixing on PAH and soot formation, four species of methane, ethane, propane and propene have been mixed in counterlfow ethylene diffusion flame. Laser-induced incandescene and laser-induced fluorescene techniques were employed to measure soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Results showed that the mixing of ethane (or propane) in ethylene diffusion flame produces more PAHs and soot than those of propene, even though the propene diffusion flame produces more PAHs and soot than that of propane and ethane. Considering that propene directly dehydrogenates to propargyl radical, this behavior implied that the enhancement of PAH and soot formation by the fuel mixing of ethylene and ethane (or propane) cannot be explained by propargyl radical directly dehydrogenated from ethane (or propane).

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Experimental Study on the Effect of DC Electric Field on Extinction Characteristics of Counterflow Diffusion Flame (대향류 확산화염의 소염특성에 미치는 직류전기장의 영향에 관한 실험적 연구)

  • Park, I.H.;Kim, M.K.;Won, S.H.;Cha, M.S.;Chung, S.H.
    • 한국연소학회:학술대회논문집
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    • 2006.10a
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    • pp.253-259
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    • 2006
  • The effect of DC electric fields on the flame extinction was investigated experimentally in counterflow configurations for the methane/oxygen/nitrogen diffusion flame. The electric fields was applied by connecting the high voltage and ground terminals to the upper and lower burners, respectively. In case of having electric fields, several modes of flame extinction was observed according to the electric field intensity and strain rate defined by the exit velocity. To visualize and characterize the flame structure and intensity, planar LIF technique was adopted for OH radicals. Consequently, several length scales, including the flame width, thickness, and height from the burner tip, were introduced to explain the various flame behaviors and to characterize the flame extinctions. It was found that the variation of flame width and the chemical reaction are strongly related to a critical electric field intensity, thus the various modes of diffusion flame extinction could be observed due to the electric fields.

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Soot and PAH Formation in Counterflow Diffusion Flames of Ethylene-Propane (에틸렌/프로판 대향류 확산화염에서 PAH 와 매연의 생성특성)

  • Yoon, Seung-Suk;Lee, Sang-Min;Hwang, Jun-Young;Chung, Suk-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.6
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    • pp.817-822
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    • 2002
  • Sooting characteristics of counterflow ethylene/propane mixture flames have been experimentally studied to investigate the fuel structure effect on PHM and soot formation. Laser-induced incandescene and laser-induced fluorescene techniques were employed to measure soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Importance of $C_{3-}$species on PAH growth as well as the H-abstraction-C$_2$ $H_2$addition (HACA) mechanism has been emphasized, considering that PAH growth rate is greater for with mixed fuel than fer pure fuel flames. It was also confirmed that HACA pathways are the dominant soot growth mechanism. A new PAH growth model including both $C_{2-}$ and $C_{3-}$growth mechanisms is proposed based on the experimental results.

An Experimental Study on the $CH_4{\;}/{\;}Air{\;}/{\;}CO_2$ Counterflow Diffusion Flame ($CH_4{\;}/{\;}Air{\;}/{\;}CO_2$ 대향류 확산화염에 대한 실험적 연구)

  • Lee, Chong-Won;Lee, Chun-Beom;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
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    • 2001.06a
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    • pp.31-45
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    • 2001
  • The effect of adding carbon dioxide to methane-air flame was investigated experimentally. Measurements included extinction limits, flame temperature and photographic investigation of flame. A diffusion flame was stabilized between counterflowing streams of methane diluted with carbon dioxide and air diluted with carbon dioxide. Extinction limits and temperature for such flames were measured over a wide parametric range and were compared with those for other flames that fuel or oxidant was diluted with nitrogen or argon. The experimental results indicate that extinction phenomena can be explained by thermal effect and as an amount of carbon dioxide in fuel or oxidant increases, greatly as compared with other flames flame-temperature falls and flame-thickness is reduced.

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Experimental Study on Behavior near Extinction in Buoyancy-minimized Counterflow Diffusion Flame (부력 효과의 최소화를 통한 소화 근처 대향류 확산화염 거동에 관한 실험적 연구)

  • Chung, Yong Ho;Park, Jeong;Kwon, Oh Boong;Yun, Jin-Han;Keel, Sang-In;Kim, Tae Hyung;Kim, Young Ju
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.23-26
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    • 2012
  • Experimental study was conducted to elucidate flame extinction phenomena in counterflow flame. Using a curtain helium flow significantly reduced buoyancy such that the flame can be positioned at the center between the upper and lower nozzles even at the velocity ratio of 1.0. The curves of critical diluent mole fraction versus global strain rate have C-shapes. The flame oscillation was observed prior to low strain rate flame extinction at both flame conditions with and without minimizing buoyancy force. The results show that, at low strain rate flame, the self-excitation frequency with the order of 1.0 Hz in the case of utilizing pure helium gradually decreases in increase of $N_2$ mole fraction in the curtain flow, meaning that buoyancy suppresses the self-excitation of the outer edge flame.

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Effect of Fuel Mixing on PAH and Soot Formation in Counterflow Diffusion Flames (다양한 연료의 혼합에 따른 대향류 확산화염에서의 PAH 및 매연생성 특성)

  • Yoon, S.S.;Lee, S.M.;Chung, S.H.
    • Journal of the Korean Society of Combustion
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    • v.8 no.3
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    • pp.8-14
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    • 2003
  • In order to investigate the effect of fuel mixing on PAH and soot formation, four species of methane, ethane, propane and propene have been mixed in counterlfow ethylene diffusion flame. Laser-induced incandescene and laser-induced fluorescene techniques were employed to measure soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Results showed that the mixing of ethane (or propane) in ethylene diffusion flame produces more PAHs and soot than those of propene. Considering that propene directly dehydrogenates to propargyl radical, this behavior implied that the enhancement of PAH and soot formation by the fuel mixing of ethylene and ethane (or propane) cannot be explained solely by propargyl radical directly dehydrogenated from ethane (or propane). Thus, combination reactions between C1 and C2-species for the formation of propargyl was suggested to identify the synergistic effect occurring in the flames of ethylene and propane (or ethane) mixtures.

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An Evaluation of a Direct Numerical Simulation for Counterflow Diffusion Flames (대향류 확산화염에 대한 직접수치모사의 검증)

  • 박외철
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.74-81
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    • 2001
  • A direct numerical simulation (DNS) was applied to nonpremixed counter-flow diffusion flames between oxidizer and fuel ducts. The objective of this study is to evaluate the numerical method for simulation of axisymmetric counterflow diffusion flames. Effects of computational domain size and grid size were scrutinized, and then the method was applied to air-methane diffusion flames. The results at zero gravity conditions were in good agreement with those obtained by the one-dimension flame code OPPDIF. It was confirmed thai the numerical method is applicable to the diffusion flames at the normal gravity conditions since the results clearly showed the effects of buoyancy and velocity ratio.

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Experimental Study on Extinction Behavior in Buoyancy-minimized Counterflow Diffusion Flame (부력 효과의 최소화를 통한 대향류 확산화염 소화거동에 관한 실험적 연구)

  • Chung, Yong Ho;Park, Jeong;Kwon, Oh Boong;Yun, Jin-Han;Kee, Sang-In;Kim, Young Ju
    • Journal of the Korean Society of Combustion
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    • v.17 no.4
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    • pp.38-43
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    • 2012
  • Experimental study was conducted to elucidate flame extinction phenomena in counterflow flame. Using a curtain helium flow significantly reduced buoyancy such that the flame can be positioned at the center between the upper and lower nozzles even at the velocity ratio of 1.0. The curves of critical diluent mole fraction versus global strain rate have C-shapes. The flame oscillation was observed prior to low strain rate flame extinction at both flame conditions with and without minimizing buoyancy force. The results show that, at low strain rate flame, the self-excitation frequency with the order of 1.0 Hz in the case of utilizing pure helium gradually decreases in increase of $N_2$ mole fraction in the curtain flow, meaning that buoyancy suppresses the self-excitation of the outer edge flame.

Chemical effects of added $CO_{2}$ and $H_{2}O$ to major flame structures and NOx emission characteristics in $CH_4$/Air Counterflow Diffusion Flames (메탄-공기 대향류확산화염에서 $CO_2$$H_2O$의 첨가가 화염구조와 NOx배출특성에 미치는 화학적 영향)

  • Hwang, Dong-Jin;Park, Jeong;Lee, Kyung-Hwan;Keel, Sang-In
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.129-136
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    • 2003
  • Numerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added $CO_{2}$ and $H_{2}O$ to fuel- and oxidizer-sides on flame structure and NO emission behavior in $CH_{4}$/Air counterflow diffusion flames. The dilution with $H_{2}O$ results in significantly higher flame temperatures and NO emission, but dilution with $CO_{2}$ has much more chemical effects than that with $H_{2}O$. Maximum reaction rate of principal chain branching reaction due to chemical effects decreases with added $CO_{2}$. but increases with added $H_{2}O$. The NO emission behavior is closely related to the production rate of OH, CH and N. The OH radical production rate increases with added $H_{2}O$ but those of CH, N decrease. On the other hand the production rates of OR CH and N decrease with added $CO_{2}$. It is found that NO emission behavior is considerably affected by chemical effects of added $CO_{2}$ and $H_{2}O$.

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Dynamic Behaviors of Oscillating Edge-Flame in Low Strain Rate Counterflow Diffusion Flames (저신장율 대향류확산화염에서 진동불안정성을 갖는 에지화염의 동적거동)

  • Park, June-Sung;Kim, Hyun-Pyo;Park, Jeong;Kim, Jeong-Soo;Keel, Sang-In
    • 한국연소학회:학술대회논문집
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    • 2006.10a
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    • pp.65-72
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    • 2006
  • Experiments in methane-air low strain rate counterflow diffusion flames diluted with nitrogen have been conducted to study the behavior of flame extinction and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conduction heat loss in addition to radiative heat loss could be remarkable at low global strain rates. Critical mole fraction at flame extinction is examined with velocity ratio and global strain rate. Onset conditions of edge flame oscillation and flame oscillation modes are also provided with global strain rate and added nitrogen mole fraction to fuel stream (fuel Lewis number). It is seen that flame length is closely relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation considerably. Edge flame oscillations in low strain rate flames are experimentally described well and are categorized into three: a growing oscillation mode, a decaying oscillation mode, and a harmonic oscillation mode. The regime of flame oscillation is also provided at low strain rate flames. Important contribution of lateral heat loss even to edge flame oscillation is clarified.

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