이중 확산 연소장에서의 오염물질 배출 특성

김종현,이근오,이창언 한국산업안전학회 2002 한국안전학회지 Vol.17 No.3

The NOx emission characteristics of double-concentric diffusion flames and normal diffusion flames fueled with CH4 were studied. Experimental and numerical investigations were carried out for double-concentric diffusion flame with varying central air flow rate and normal diffusion flame. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by numerical model based on detailed chemistry. From the comparison between double-concentric diffusion flames and normal diffusion flames, the results show that EINOx of double-concentric diffusion flames are lower than normal diffusion flame, because of Prompt EINOx was decreased. EINOx of double-concentric diffusion flames increase with central air flow rate increasing.

프로판 확산화염의 불안정성에 대한 내부화염의 역할

남연우(Younwoo Nam),문두성(Dusung Moon),이원남(Wonnam Lee) 한국연소학회 2009 KOSCOSYMPOSIUM논문집 Vol.- No.39

The instability of laminar propane diffusion flames due to the existence of an inner inverse diffusion flame has been investigated using a concentric co-flow burner. A stable laminar propane diffusion flame started to oscillate with a small amount of air flow through an inner nozzle. Further increase of air flow rate changed the flame into a stable non-sooting, an oscillating and sooting, an oscillating non-sooting, and a stable non-sooting flame in sequence. Starting from high air flow rate, the decrease of air flow rate changed the flame back to a stable non-sooting flame via an oscillating non-sooting, an oscillating sooting and an oscillating non-sooting flame. The increased or decreased soot formation and oxidation rates, radiation heat loss, and heating by an inner flame are most likely to be responsible for the characteristics of a propane diffusion flames on instability and soot production.

내부로 공급되는 공기 유량에 따른 에틸렌 확산화염의 매연 방출 현상

남연우(Younwoo Nam),문두성(Dusung Moon),이원남(Wonnam Lee) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41

The characteristics of soot formation with air addition have been studied experimentally using a concentric co-flow diffusion burner, which provides the stratified air mixture through an inner nozzle. Integrated soot volume fraction, temperature and scattering images of diffusion flames were measured using a laser light extinction method, two-color pyrometry and 2-D laser light scattering technique, respectively. An ethylene diffusion flame started to emit soot with a small amount of air flow through an inner nozzle, which could be explained with the enhanced soot formation process due to the oxygenated species assisted pyrolysis. The increase of air flow rate up to 250 sccm transformed a soot emitting flame into a non-emitting flame without inner flame. Further increase of air flow rate created an inner flame and changed the flame into a soot emitting flame. When air flow rate was decreased again, the flame was changed back to a emitting flame; however, the presence of an inner flame altered the soot formation and oxidation characteristics of the flame and enhanced the soot formation process. The oxygenated species assisted pyrolysis, the radiation heat loss and the temperature effect of inner flames would determine the characteristics of soot production/oxidation of an ethylene diffusion flame with air flow inside.

Preferential diffusion effects in downstream interactions between premixed H₂–air and CO–air flames

Kim, Young Ju,Kim, Tae Hyung,Park, Jeong,Kwon, Oh Boong,Keel, Sang In,Yun, Jin Han Elsevier 2014 Fuel Vol.116 No.-

<P><B>Abstract</B></P> <P>The effects of preferential diffusion of hydrogen in downstream interacting counterflow H<SUB>2</SUB>–air and CO-flames were investigated using numerical simulations. The global strain rate was varied in the range 30–5917s<SUP>−1</SUP>, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures with a mixed average diffusivity with those where the diffusivities of H, H<SUB>2</SUB> and N<SUB>2</SUB> were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of H<SUB>2</SUB> and CO as a function of the strain rate. The main oxidation route for CO is CO+O<SUB>2</SUB> →CO<SUB>2</SUB> +O, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely CO+OH→CO<SUB>2</SUB> +H, can be made available, provided that hydrogen from the H<SUB>2</SUB>–air flame can penetrate the CO–air flame. This modifies the flame characteristics in the downstream interaction between the H<SUB>2</SUB>–air and CO–air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to exhibit anomalous behavior with a much stronger dependence on the interaction between the two flames. Such anomalous behavior includes a partial opening of the upper lean extinction boundary in the interaction between a lean H<SUB>2</SUB>–air flame and a lean CO–air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich H<SUB>2</SUB>–air flame and a lean CO–air flame. At large strain rates, there are two conditions where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Impact of chemical interaction through preferential diffusion of H<SUB>2</SUB> in flame structure. </LI> <LI> Comparison between flame characteristics with and without restricting diffusivity of H<SUB>2</SUB>. </LI> <LI> Modifying chemical time in CO oxidation through preferential diffusion of H<SUB>2</SUB>. </LI> </UL> </P>

다중 동축류 화염의 구조와 특성

문두성(Dusung Moon),이원남(Wonnam Lee) 한국연소학회 2009 KOSCOSYMPOSIUM논문집 Vol.- No.39

A multi-concentric co-flow burner was designed and constructed in order to study the flame-flame interaction in a diffusion flame scheme. A variety of multiple ethylene diffusion flames could be obtained up to a quadruple flame that contains two inverse diffusion flames and two normal diffusion flames. Flames may be either merged together or separated each other. A lifted inner flame was formed with relatively higher air flow rate while an attached inner flame was formed with lower air flow rate. The amount of soot in a flame decreases with a lifted inner flame although the apparent flame temperature seems to be increased. An attached inner flame, however, increases the amount of soot in a diffusion flame until that the size of inner flame becomes very small. The possibility of experimental investigations for the flame-flame interaction has been demonstrated.

환형 화염이 있는 다중 에틸렌 확산화염의 PAH 및 매연분포

문두성(Dusung Moon),남연우(Younwoo Nam),이원남(Wonnam Lee) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41

The distributions of PAH and soot particles were measured for multi-concentric ethylene diffusion flames with an annular flame inside and with an inverse diffusion flame attached at the center nozzle in addition to an annular flame. Temperatures of soot particles in flames were also measured by a modulated LⅡ technique. The presence of an annular flame inside increased the flame temperature at the soot formation region and resulted in the increase of PAH and soot concentrations. The maximum soot volume fraction, however, was decreased mostly due to the rapid oxidation of soot particles at the soot oxidation region. The addition of an inverse diffusion flame inside of an annular flame significantly decreased PAH and soot concentrations all over the flame. The oxidation of soot precursors including PAH as well as significantly increased flame temperature due to the flame-flame interaction could be the primary reason for the decreased soot volume fraction with annular and inverse diffusion flames inside.

상호작용 하는 H₂-공기/CO-공기 예혼합화염에 미치는 H₂ 선호 확산 영향에 대한 수치적 연구

정용호(Yong Ho Chung),박정(Jeong Park),권오붕(Oh Boong Kwon),길상인(Sang In Keel),윤진한(Jin Han Yun) 한국연소학회 2013 한국연소학회지 Vol.18 No.4

The effects of preferential diffusion of hydrogen in interacting counterflow H₂-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range 30-5917 s<SUP>-1</SUP>, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, H₂ and N₂ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of H₂ and CO as a function of the strain rate. The main oxidation route for CO is CO + O₂ → CO₂ + O, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely CO + OH → CO₂ + H, can be significant, provided that hydrogen from the H₂-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the H2-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean H2-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich H₂-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

상호작용 하는 H₂-공기/CO-공기 예혼합화염에 미치는 H₂ 선호 확산 영향에 대한 수치적 연구

정용호,박정,권오붕,길상인,윤진한,Chung, Yong Ho,Park, Jeong,Kwon, Oh Boong,Keel, Sang In,Yun, Jin Han 한국연소학회 2013 한국연소학회지 Vol.18 No.4

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

부상 예혼합화염이 있는 확산화염의 매연 생성 및 산화 메커니즘

문두성(Dusung Moon),남연우(Younwoo Nam),이원남(Wonnam Lee) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40

The soot formation and oxidation mechanisms of laminar ethylene diffusion flames have been experimentally studied at the presence of inner flames. The inner flame was either an inverse diffusion flame (IAF) that is attached at the center nozzle or a lifted premixed flame (ILF). The soot volume fraction profiles were obtained by a laser light extinction technique with an Abel inversion. The soot particle temperature profiles were measured by a modulated LII technique. The flame/soot particle temperatures were increased due to the presence of inner flames for both IAF and ILF cases. However, soot volume fraction at the center region was increased at the presence of an IAF while they were decreased with an ILF. The additional soot particles and PAH's that are supplied due to the nature of an inverse diffusion flame of IAF and the increased temperature for the soot formation region could be main reasons for the increase soot volume fraction. The additional soot oxidation region due to the nature of a premixed flame of ILF at the center region and the increased temperature at the soot oxidation region could be responsible for the decreased soot volume fraction.

층류확산화염의 불안정성에 대한 매연생성 특성의 역할

남연우(Younwoo Nam),이원남(Wonnam Lee) 한국연소학회 2010 한국연소학회지 Vol.15 No.3

In this study, soot formation characteristics on the instability of laminar diffusion flames were investigated experimentally using a concentric co-flow burner. When a small amount of air was supplied through an inner nozzle, a stable propane laminar diffusion flame became unstable and began to oscillate mainly due to the dilution effect. The increase of air flow rate transformed an oscillating non-sooting flame into a stable nonsooting flame. When the air flow rate was continuously increased an inner flame was formed and the flame was changed to an oscillating sooting flame, an oscillating non-sooting flame and finally a stable non-sooting hollow flame. When the air flow rate was decreased, a non-sooting hollow flame was eventually changed back to a stable non-sooting flame. The presence of an inner flame, however, altered the soot formation characteristics of a flame. More soot production was observed with the presence of an inner flame. The increased or decreased soot formation/oxidation rates, the radiation heat loss, and the heating effect of inner flames are most likely to be responsible for the observed instability of laminar diffusion flames.