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압력용기를 이용한 확산화염의 매연 생성율 및 산화율에 관한 실험
배승만(Seungman Bae),남연우(Younwoo Nam),이원남(Wonnam Lee) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
Soot formation and oxidation processes have been studied experimentally at the elevated pressures up to 3 atm. Dilution air in the propane fuel flow controlled the flame size and shape compatible for all pressure conditions. The overall oxidation rate of soot is not noticeably changed with pressure when the size and shape of flames are similar. Since the mass diffusivity is inversely proportional to the pressure and the density of oxygen is proportional to the pressure, the oxygen mass transfer rate to the soot oxidation region is not expected to change with pressure unless the pressure is very high. The soot oxidation reaction is most likely to be mass transfer controlled; and therefore, the similar overall oxidation rates were observed at 1, 2, and 3 atm in flames, whose size and shape are compatible.
확산화염의 PAH LIF 신호 측정에 대한 LII 간섭
배승만(Seungman Bae),이상구(Sanggu Lee),안태국(Taekook Ahn),이원남(Wonnam Lee) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
The LII interference on the measurement of PAH LIF signal from a diffusion flame with 488 ㎚ wavelength Argon-ion laser excitation has been experimentally investigated. The signals measured in the region, where soot particles do not exist, can be interpreted as PAH LIF signals. However, in the region, where soot particles exist, the measured signals should be mostly considered as Mie scattering signals and/or LII signals depending on the measurement condition. In the region, where soot particles and PAH’s co-exist, the detection of PAH LIF signals would be difficult if not impossible with current measurement techniques.
화염의 유동장과 온도에 따른 동축류 확산화염의 불안정 특성
남연우(Younwoo Nam),배승만(Seungman Bae),이원남(Wonnam Lee) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40
Flow and temperature characteristics were investigated when co-flow diffusion flames become unstable. Soot concentration, temperature and velocity profiles of diffusion flames were measured using a laser light extinction method and modulated LII signals near the smoke-points or unstable conditions. For methane and ethane diffusion flames, soot concentration is low and flame temperature remains high, and therefore, the flame becomes unstable when the fuel flow rate increases. For ethylene and propylene diffusion flames, however, soot concentration is high and flame temperature becomes low, and the flame starts to emit soot before it becomes unstable with the increase of fuel flow rate. For propane and n-butane diffusion flames, the flame becomes unstable and emits soot at the same time when the fuel flow rate is increased. When soot concentration becomes high, the increased radiation heat loss lowers the flame temperature, and therefore, the flame tends to emit soot before it reaches to the unstable condition. On the other hand, when the soot concentration in a flame is low, the flame temperature remains high since the radiation heat loss is less. As a result, the flame can be long enough to become unstable or the flow velocity can be accelerated fast enough to develop the instability.
자기장 분포가 확산화염의 연소특성에 미치는 영향: 자기장 On/Off 주기와 Duty Ratio의 역할
이원남(Wonnam Lee),배승만(Seungman Bae) 한국연소학회 2012 한국연소학회지 Vol.17 No.1
The influence of magnetic field on propane and acetylene diffusion flames have been experimentally investigated using an electromagnetic system. Periodically induced magnetic field having various frequencies and duty ratios was established in square wave form. The maximum intensity and gradient of magnetic field were 1.3 T and 0.27 T/mm, respectively. The width of a propane flame was reduced up to 4.5% and the brightness was enhanced up to 25% when the magnetic field was induced. The soot emission from an acetylene flame was ceased when magnetic field was induced. The alteration of flow field, which is due to the paramagnetic characteristics of oxygen molecule, is most likely to be responsible for the change in flame size and brightness. The effect of magnetic field on diffusion flames, which competes with the gravitational effect, was more apparent from a smaller size flame. The magnetic field effect, therefore, could be important under microgravity conditions. Since the time required to alter the flow field must be finite, the magnetic field effect is likely to be less significant for a periodically oscillating magnetic field at a high frequency or having a small duty ratio.
주기적으로 반복되는 자기장이 프로판 마이크로 화염에 미치는 영향
이원남(Wonnam Lee),배승만(Seungman Bae) 한국연소학회 2009 KOSCOSYMPOSIUM논문집 Vol.- No.39
The effects of periodic magnetic field on a propane micro flame have been experimentally investigated utilizing an electromagnetic system. Square wave periodic magnetic fields having various frequencies and duty ratios were established. The electromagnetic system produced a field of up to 1.3 Tesla and the maximum gradient up to 250 T/m at the flame location. The flame size was reduced up to 20 % in volume and the brightness was increased up to 25 % with the existence of magnetic flux. The change in flow field is most likely to be responsible for the change in flame size and brightness. The magnetic flux effect, which competes with the gravitational effect, was more significant on a smaller flame. The effect of magnetic flux, therefore, could do important role under microgravity conditions. Since the time required to alter the flow field should be finite, the effect of magnetic flux is likely to be less significant for a periodic magnetic field with high enough frequencies or very small duty ratios.
아르곤이온 레이저를 이용한 확산화염 내 PAH의 LIF 신호 측정에 LII 신호가 미치는 영향
안태국(Taekook Ahn),배승만(Seungman Bae),이원남(Wonnam Lee),박선호(Sunho Park) 한국연소학회 2018 한국연소학회지 Vol.23 No.1
The effect of LII interference on the measurement of LIF signals from PAH in a diffusion flame has been investigated. Argon-ion laser at 488 nm was vertically or horizontally polarized, and irradiated to the centerline of the flame at varying flame height. Signals from PAH-rich regions measured at 515 nm were mostly LIF signals, however, signals from soot-rich regions were determined to be mixed with Mie scattering signals and/or LII signals. Signals measured 1 mm above the excitation height were mostly LII signals from soot particles. The results show that a quantitative determination of the LIF’s contribution to the measured signals would be difficult as long as the experimental setup described here is used for the regions where PAHs and soot particles exist together.