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정석호(Chung S. H.),원상희(Won S. H.) 한국가시화정보학회 2004 한국가시화정보학회지 Vol.2 No.1
Several visualization techniques of laser diagnostics are presented for combustion phenomena. including Mie scattering for flow, Rayleigh and Raman scattering spectroscopy for major species, laserinduced fluorescence for minor species, and laser-induced incandescence for soot. These techniques have been applied to understand the various combustion phenomena more clearly, including buoyancy-dominant flow system, diffusion flam oscillation, laminar and turbulent lifted flames, flame propagation along a vortex ring, and soot zone characteristics. The usefulness of laser diagnostics on a better understanding of physical mechanism is demonstrated.
최상규(S. K. Choi),원상희(S. H. Won),정석호(S. H. Chung),차민석(M. S. Cha),송영훈(Y. H. Song) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Characteristics of syngas combustion was studied numerically for various mixing ratios of methane and syngas which was produced by partial oxidization of methane. Ideal case in which CH₄ is completely decomposed into CO and H₂, and the syngas obtained by equilibrium code which contains other species, were compared. For ideal case, the composition of premixture varies almost linearly for reforming rate, while the composition of syngas from equilibrium code varies nonlinearly and does not vary much until the reforming rate of 0.4. When the mixture of ambient temperature was used, as reforming rate increases, flame temperature decreases but laminar burning velocity increases. This inverse trend which is not general is due to the decrease of overall activation energy as reforming rate. The exponential term of the reaction rate which contains the activation energy and temperature shows similar trend to the laminar burning velocity. Lean flammability limit is expanded, and extinction stretch rate of diffusion flame is increased as reforming rate increases. The flame characteristics is more improved for the ideal case, it will be important to reform effectively to achieve better performance of combustor.
원추형 공동과 분사공을 이용한 단발 레이저 유도에 의한 다점점화
류승관(S. K. Tyu),원상희(S. H. Won),정석호(S. H. Chung) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study, an advanced laser-induced multi-point ignition technique with a single-shot laser is proposed. This ignition technique has been experimentally investigated in the constant-volume chamber filled with methane/air premixture by means of high speed shadowgraph for visualization of flame spread and pressure recording. Each a conical cavity opened near the apex and a closed conical cavity is installed on the prechamber and main chamber, respectively which is aligned with the path oflaser beam. And two jet-holes are installed on the top and bottom of the prechamber. Two ignition points are occurred at the conical cavities because of laser-induced ignition and hot gaseous jets from prechamber cavity and two jet-holes occur three ignition point.<br/> This result shows that this ignition technique has an advantage of significant reduction of total combustion time and flame initiation period, and exhibits more rapid and a higher maximum pressure rise than another laser-induced ignition technique.
교류전기장이 인가된 상태에서 전선을 통해 전파하는화염에 대한 전선직경의 영향
박순호(S. H. Park),임승재(S. J. Lim),권오붕(O. B. Kwon),박정(J. Park),정석호(S. H. Chung) 한국연소학회 2017 한국연소학회지 Vol.22 No.3
An experimental study on spreading flame over electrical wire, which was insulated by Polyethylene(PE) and had different diameters, was conducted with applied AC electric field. The result showed that the flame spread rate decreased in increase of the diameter of insulator at a fixed electric field. The flame spread rate exhibited increase or decrease tendency with applied AC electric field, having three distinct regimes depending on applied voltage and frequency. In each regime, the flame spread rate was characterized by physical parameters of applied electric fields and wire dimensions, and the behaviors could be explained by a thermal balance mechanism.
직류전기장이 인가된 상태에서 쌍둥이 전선을 통해 전파하는 화염들에 대한 상호작용
박순호(S. H. Park),김희준(H. J. Kim),권오붕(O. B. Kwon),박정(J. Park),정석호(S. H. Chung) 한국연소학회 2018 한국연소학회지 Vol.23 No.2
The effect of a direct current (DC) electric field on the characteristics of flame spread over polyethylene (PE) -insulated twin electrical wires was studied by varying wire gap (S) and voltage (VDC). The flame spread rate (FSR) for the wire with negative voltage (SF-) was larger than with positive voltage (SF+) initially and becomes the same in developed region. The FSR could be classified into two regimes; twin flame spread and single flame spread after the extinction of positive voltage (SF+). In each regime, three sub-regimes are identified depending on S and VDC. In each regime, FSR could be characterized by S and VDC The variation of FSR was explained by thermal balance mechanism with ionic wind effect. In high intensive of voltage, the flames were extinguished, at excessive voltages, an electrical short occurred.
전기장이 튜브내 예혼합화염 전파속도에 미치는 영향에 관한 연구
류승관(S. K. Ryu),원상희(S. H. Won),차민석(M. S. Cha),정석호(S. H. Chung) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
The effect of electric fields on flame speed has been investigated experimentally by observing propagating premixed flames in a tube for methane/air mixtures. The flame speeds were measured in both the normal and micro gravity conditions to substantiate the measurements. The results show that the flame speeds were enhanced by both the AC and DC electric fields, as the flame approached to the high voltage electrode located on the one end of the tube. The enhancement of flame speed was proportional to the square root of the electric field intensity, defined as the voltage applied divided by the distance of flame from the high voltage electrode, when the electric field intensity is sufficiently large. When the electric field intensity was low, there existed critical intensities, below which the electric fields did not influence the flame speed. This critical electric field intensity correlated well with the flame speed.