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레이저 유도 공동 점화 방식을 이용한 예혼합기 연소 특성 향상
모하메드 하산(Hassan Mohamed),고영성(Youngsung Ko),정석호(Sukho Chung) 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.6
In this study. a new type of laser-induced ignition using a conical cavity has been developed<br/> to utilize all the available incident laser energy. In the method, it is possible to ignite<br/> combustible methane/air mixtures by directing a laser beam of a constant small diameter into a small conical cavity, without focusing the laser beam. Shadowgraphs for the early stage of combustion process show that a hot gas jet is ejected from the cavity, especially with lean mixture. After a very short time. the hot gas jet finishes issuing and the flame behavior is quite similar to flame propagation initiated by a conventional spark ignition. The combustion process using the new method exhibits more rapid pressure increase and a higher maximum pressure rise than that of the center ignition using laser-induced spark, with significant decrease in the combustion time. Also, the new ignition method is numerically modeled to simulate the flame kernel development and subsequent combustion process using the KIVA-II code. The calculated results show satisfactory agreement with experimental results.<br/>
최병철(Byungchul Choi),김길남(Gilnam Kim),정석호(Sukho Chung) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Characteristics of laminar lifted flames for highly diluted propane with nitrogen have been investigated in various co-flow temperatures up to 1000 K, including the behaviors of liftoff height and liftoff velocity. When the co-flow temperature was above 940 K, the flame was auto-ignited at a certain height above fuel nozzle tip, which exhibited unique characteristics as compared to the laminar lifted flames for T?≤900K. When the flame was auto-ignited, it is faint and colors weak blue such as mild combustion at high temperature. As increasing initial temperature in the autoignition range, the ignition delay time exponentially decreases and the propagation speed almost linearly increases. Consequently, based on the balance mechanism for the stabilization of laminar lifted flame, the jet velocity to make a lifted flame in the auto-ignition temperature range should be exponentially increased. By the way, the jet velocity range for the balance mechanism could be steadily decreased and finally disappeared by increasing initial temperature.
[가솔린엔진부문] 연료/산화제의 2차원 혼합층에서 삼지화염의 전파 특성에 관한 수치해석
김준홍(Junhong Kim),김홍집(Hongjip Kim),정석호(Sukho Chung) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Propagation characteristics of tribrachial flames have been studied numerically in two-dimensional mixing layer. The flow redirection effect at the leading edge of a tribrachial flame increases the flame speed beyond the corresponding laminar burning velocity. By using the fact that a mixture fraction gradient increases as a tribrachial flame propagates toward upstream region in a mixing layer, the effect of mixture fraction gradient is studied. Results show that the propagation speed of tribrachial flame increases with increasing Damkohler number and decreasing mixture fraction gradient.
윤승석(Seungsuk Yoon),이상민(Sangmin Lee),정석호(Sukho Chung) 한국자동차공학회 2005 한국 자동차공학회논문집 Vol.13 No.3
In order to investigate the effect of dimethyl ether (DME) on PAH and soot formation, the fuel has been mixed to the counter-flow diffusion flames of ethylene. Laser-induced incandescence and laser-induced fluorescence techniques were employed to measure relative concentrations of soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Results showed that even though pure DME flame produces the minimal amount of PAH and soot, the mixture fuel of DME and ethylene could increase PAH and soot formation, as compared to those of pure ethylene flame. This implies that even though DME has been known to be a clean fuel for soot formation, the mixture fuel of DME and the hydrocarbon fuel could produce enhanced production of soot. Numerical simulation demonstrated that methyl (CH₃) radical generated by the initial pyrolysis of DM E can be contributed to the enhancement of PAH and soot formation, through the formation of propargyl (C₃H₃ ) radical.
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.
폴리에틸렌으로 피복된 기울어진 전선을 통한 화염전파에 대한 실험적 연구
임승재(Seungjae Lim),박정(Jeong Park),김민국(Minkuk Kim),정석호(Sukho Chung),Fusita Osamu 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12
The Experimental study on flame spread over Polyethylene insulated slanted electrical wire was conducted with applied AC electric field. The results showed that flame slanted toward burnt side with AC electric field and slanted angle. The flame spread rate decreased with AC electric field, decreased initially with slanted angle and increased for high slanted angle. Flame extinction was characterized by applied voltage and frequency. Variation of spread rate could be explained by thermal balance mechanism.