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H<sub>2</sub>-공기와 CO-공기의 예혼합화염의 화염소화에 있어서 화학적 상호작용의 효과
정승욱,박정,권오붕,길상인,윤진한,Jung, Seongwook,Park, Jeong,Kwon, Ohboong,Keel, Sangin,Yun, Jinhan 한국연소학회 2013 한국연소학회지 Vol.18 No.4
Important role of chemical interaction in flame extinction was numerically investigated in downstream interaction among lean(rich) and lean(rich) premixed as well as partially premixed $H_2$-air and CO-air flames. The strain rate varied from 30 to $5917s^{-1}$ until interacting flame could not be sustained anymore. Flame stability diagrams mapping lower and upper limit fuel concentrations for flame extinction as a function of strain rate are presented. Highly stretched interacting flames were survived only within two islands in the flame stability map where partially premixed mixture consisted of rich $H_2$-air flame, extremely lean CO-air flame, and a diffusion flame. Further increase in strain rate finally converges to two points. Appreciable amount of hydrogen in the side of lean $H_2$-air flame also oxidized the CO penetrated from CO-air flame, and this reduced flame speed of the $H_2$-air flame, leading to flame extinction. At extremely high strain rates, interacting flames were survived only by a partially premixed flame such that it consisted of a very rich $H_2$-air flame, an extremely lean CO-air flame, and a diffusion flame. In such a situation, both the weaker $H_2$-air and CO-air flames were parasite on the stronger diffusion flame such that it could lead to flame extinction in the situation of weakening the stronger diffusion flame. Particular concerns are focused on important role of chemical interaction in flame extinction was also discussed in detail.
상호작용하는 H₂-CO 예혼합 화염에서 H₂선호확산의 영향에 관한 수치적 연구
오상훈(Sanghoon Oh),박정(Jeong Park),권오붕(Ohboong Kwon) 한국연소학회 2012 한국연소학회지 Vol.17 No.3
The effects of strain rate and preferential diffusion of H2 on flame extinction are numerically studied in interacting premixed syngas-air flames with fuel compositions of 50% H₂ + 50% CO and 30% H₂ + 70% CO. Flame stability diagrams mapping lower and upper limit fuel concentrations at flame extinction as a function of strain rate are examined. Increasing strain rate reduces the boundaries of both flammable lean and rich fuel concentrations and produces a flammable island and subsequently even a point, implying that there exists a limit strain rate over which interacting flame cannot be sustained anymore. Even if effective Lewis numbers are slightly larger than unity on extinction boundaries, the shape of the lean extinction boundary is slanted even at low strain rate, i.e. ag = 30 s<SUP>-1</SUP> and is more slanted in further increase of strain rate, implying that flame interaction on lean extinction boundary is strong and thus hydrogen (as a deficient reactant) Lewis number much less than unity plays an important role of flame interaction. It is also shown that effects of preferential diffusion of H2 cause flame interaction to be stronger on lean extinction boundaries and weaker on rich extinction boundaries. Detailed analyses are made through the comparison between flame structures with and without the restriction of the diffusivities of H2 and H in symmetric and asymmetric fuel compositions. The reduction of flammable fuel compositions in increase of strain rate suggests that the mechanism of flame extinction is significant conductive heat loss from the stronger flame to ambience.
H₂-공기와 CO-공기의 예혼합화염의 화염소화에 있어서 화학적 상호작용의 효과
정승욱(Seongwook Jung),박정(Jeong Park),권오붕(Ohboong Kwon),길상인(Sangin Keel),윤진한(Jinhan Yun) 한국연소학회 2013 한국연소학회지 Vol.18 No.4
Important role of chemical interaction in flame extinction was numerically investigated in downstream interaction among lean(rich) and lean(rich) premixed as well as partially premixed H₂-air and CO-air flames. The strain rate varied from 30 to 5917 s<SUP>-1</SUP> until interacting flame could not be sustained anymore. Flame stability diagrams mapping lower and upper limit fuel concentrations for flame extinction as a function of strain rate are presented. Highly stretched interacting flames were survived only within two islands in the flame stability map where partially premixed mixture consisted of rich H₂-air flame, extremely lean CO-air flame, and a diffusion flame. Further increase in strain rate finally converges to two points. Appreciable amount of hydrogen in the side of lean H₂-air flame also oxidized the CO penetrated from CO-air flame, and this reduced flame speed of the H₂-air flame, leading to flame extinction. At extremely high strain rates, interacting flames were survived only by a partially premixed flame such that it consisted of a very rich H₂-air flame, an extremely lean CO-air flame, and a diffusion flame. In such a situation, both the weaker H₂-air and CO-air flames were parasite on the stronger diffusion flame such that it could lead to flame extinction in the situation of weakening the stronger diffusion flame. Particular concerns are focused on important role of chemical interaction in flame extinction was also discussed in detail.
한종규(Jongkyu Han),윤성환(Sunghwan Yoon),박정(Jeong Park),권오붕(Ohboong Kwon),김태형(Taehyung Kim),박종호(Jongho Park) 한국연소학회 2012 한국연소학회지 Vol.17 No.1
Experimental study on comparison of diffusive-thermal self-excitation with buoyancy-driven one due to accumulation of partially premixed, preheated mixture in front of edge flame was conducted in horizontally and vertically injected laminar free-jet flames with an applied DC electric field of -10 kV. The application of horizontal injection method with the DC electric field to jet flames was experimentally designed to suppress heat-loss-induced self-excitation and thereby to highlight the definite difference between both diffusive-thermal and buoyancy-driven self-excitations with the same order of O(1.0 Hz), in that diffusive-thermal self-excitation has not been so far found experimentally in laminar jet flames. Flame stability maps in vertically and horizontally injected jet flames are presented. The distinct modes of individual self-excitation are shown to be well described by their own phase diagrams. The results show that buoyancy-driven self-excitation due to the accumulation of partially premixed, preheated mixtures in front of edge flame is branched from the buoyancy-induced self-excitation with O(10 Hz) due to a flame flicker. Once the buoyancy-driven self-excitation appears, it suppresses buoyancy-induced as well as diffusive-thermal self-excitation. The key characteristics for individual self-excitation are discussed and their functional dependencies of Strouhal number upon related physical parameters are also presented.
보일러 송풍기 내부 형상 변화에 따른 유동 특성에 관한 연구
이영태(YoungTae LEE),장성호(SungHo JANG),이주용(JooYong LEE),권오붕(OhBoong KWON),임희창(HeeChang LIM) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
This study has been conducted to enhance the performance of a centrifugal blower inside condensing gas boiler. In order to increase the outlet flow rate, the flow characteristics inside the blower were investigated and the case shape of the blower was modified and tested numerically and experimentally. In this study, it has been mainly focused on the flow characteristics inside the air blower and at the exit. The results are all compared with the experiment.
교류전기장이 인가된 전선을 통해 전파하는 화염에 있어서 기울어진 각도가 미치는 영향에 대한 실험적 연구
임승재(Seungjae Lim),김민국(Minkuk Kim),박정(Jeong Park),권오붕(OhBoong Kwon),정석호(Sukho Chung),Osamu Fujita 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.12
An experimental study on downwardly and upwardly spreading flames over slanted electrical wire, which is insulated by Polyethylene(PE), was conducted with applied AC electric field. The result showed that downwardly and upwardly spreading flames with angle of inclination leaned toward burnt side and unburned side, respectively. With applied AC electric fields, size of downwardly spreading flame decreased slightly and that of upwardly spreading flame increased significantly. Flame spread rate showed various trends in terms of inclination, applied voltage and frequency.
층류 동축류 제트 부상화염에서 소화한계 근처에서의 화염 거동
오수현(Suhyeon Oh),반규호(Kyuho Van),박정(Jeong Park),권오붕(Ohboong Kwon),김세원(Sewon Kim),정석호(Sukho Chung) 한국연소학회 2019 한국연소학회지 Vol.24 No.1
Characteristics of laminar lifted flames in coflow-jet of propane with helium-diluted coflowing air have been studied experimentally and numerically. Two distinct self-excitations existed: a buoyancy-driven self-excitation and a self-excitation with capsized flame near flame extinction. In particular, the flame dynamics for the latter flame were related to buoyancy effects caused by the difference in the densities between the fuel and coflow streams. To identify the mechanism of capsized flame, Mie-scattering technique, OH radical and numerical simulation of cold and reacting flow were performed.
AC 전기장이 인가된 구리 전선을 통해 전파하는 화염에 대해 피복재의 두께에 따른 화염 거동에 대한 실험적 연구
강민성(Minsung Kang),유춘상(Chunsang Yoo),박정(Jeong Park),정석호(Sukho Chung),권오붕(Ohboong Kwon) 한국연소학회 2020 한국연소학회지 Vol.25 No.4
Effects of insulation thickness on flame spread over electrical copper wires with applied AC electric fields were experimentally investigated. The AC volrage and frequency varied in ranges of 0-5 kV and 10-1000 Hz, respectively. A one electrode configuration was used such that the electric potential was applied to one wire end and thus the infinite ambience could be a ground. The results showed that the flame shape and the tilting direction were significantly influnced by applied voltage and frequency. The flame spread rate decreased in an increase of insulation thickness as well as varied sensitively with applied voltage and frequency. Additionally, the molten polyethylene (PE) experienced various dynamic behaviors such as dripping of molten PE, electrospray, di-electro-phoresis, and rotation of molten PE, essentially affecting the flame spread rate. These complicated phenomena were systematically analyzed and discussed.