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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.
일반 및 무중력에서 부상 화염의 진동 특성에 관한 연구
원상희(S. H. Won),김준홍(J. Kim),신무경(M. K. Shin),정석호(S. H. Chung),O. Fujita,T. Mori,J. H. Choi,K. Ito 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Characteristics of oscillating lifted flames in coflow have been investigated experimentally with highly<br/> diluted propane in normal and micro gravities to elucidate the stabilization mechanism. In normal gravity,<br/> oscillating lifted flames with the frequency of 2-5 Hz were observed in a certain range of fuel mole fraction<br/> and jet velocity. The oscillation frequency correlated well with jet velocity in terms of Strouhal number,<br/> defined with the stoichiometric laminar burning velocity. This demonstrated the importance of the<br/> propagation characteristics of tribrachial flames at the base of lifted flames in the flame oscillation.<br/> Microgravity experiments have been conducted after the oscillating lifted flames are stabilized in normal<br/> gravity. During the change in gravitational acceleration, the flames rapidly stabilized as nozzle attached<br/> flame mode and became stationary. This behavior confirmed that the lifted flame oscillation in normal<br/> gravity is due to the buoyancy driven instability. Numerical simulation has also been performed<br/> accounting the change in gravitational acceleration. The results successfully predicted the transition<br/> behavior from oscillating lifted flame in normal gravity to stationary attached flame in microgravity and the<br/> variation of flame shapes during the transition.
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.
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.
대향류 확산화염의 소염특성에 미치는 직류전기장의 영향에 관한 실험적 연구
박익형(I. H. Park),김민국(M. K. Kim),원상희(S. H. Won),차민석(M. S. Cha),정석호(S. H. Chung) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
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.
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.