연료에 따른 층류 예혼합화염의 CH* Chemiluminescence 신호특성 변화

이원남(Wonnam Lee),강석민(Sukmin Kang) 한국연소학회 2008 한국연소학회지 Vol.13 No.2

The CH* chemiluminescence of premixed flames and their dependency on fuel types has been experimentally investigated on laminar methane and propane premixed flames. The measured chemiluminescence intensities are observed linearly proportional to the fuel flow rate, which could be interpreted as the CH* chemiluminescence signal is linearly proportional to the heat release rate under fuel lean conditions. The effect of equivalence ratio could be expressed by an exponential function as ICH*∝α₁ exp(?₁Φ), where α₁=0.00054 and ?₁=4.60 for methane and α₁=0.0056 and ?₁=5.02 for propane. Oscillating flames showed the temporal fluctuation of chemiluminescence intensity: however, the time averaged values are virtually identical to those of quiescent flames under the same fuel flow rate and equivalence ratio conditions. This observation suggests that there is no significant flame stretch effect on chemiluminescence intensity, in average values.

동축류 확산화염의 매연생성에 미치는 연료에 첨가된 산화제의 영향

이원남(Wonnam Lee) 한국연소학회 1998 한국연소학회지 Vol.3 No.1

측정방법에 따른 에틸렌 확산화염의 온도분포

이원남(Wonnam Lee),나용대(Yong Dae Na),이범기(Bumky Lee),박승남(Seong Nam Park) 한국연소학회 2000 KOSCOSYMPOSIUM논문집 Vol.- No.-

성층화된 화염을 이용한 희박 예혼합화염의 날림 특성 제어

이원남(Wonnam Lee),안태국(Taekook Ahn),남연우(Younwoo Nam) 한국연소학회 2012 한국연소학회지 Vol.17 No.4

The Blow-off characteristics of LPG/air lean pre-mixed flames were experimentally investigated using a double and a multiple concentric coflow burners. Experiments were conducted to understand the effects of recirculation motion, thermal interaction between flames, and stratified flame configuration. Here, the stratified premixed flame is a “ew concept”of a flame that sequentially contains fuel rich, stoichiometric, and fuel lean reaction zones in a flame. The blow-off from a lean premixed flame was significantly suppressed with recirculation motion. The recirculation motion by itself, however, was not sufficient to prevent the blowoff when the equivalence ratio became low. The existence of a inner premixed flame could also help to prevent the blow-off of lean premixed flame; however, the blow-off suppression effect was rather diminished by weakened recirculation motion with the presence of inner flame. The inner flame could be separated from an outer flame on a multiple concentric coflow burner, causing recirculation motion as well as thermal interaction between flames to become effective; therefore, the blow-off was further suppressed. The lean premixed flame could be stabilized with a fuel rich premixed flames that was produced with the supply of fuel through an inner nozzle. The penetration of lean premixed gas from outside into the fuel stream produced a lifted rich premixed flame. Chemiluminescence images of OH, CH, and C2 radicals confirmed the structure of a stratified premixed flame. The stable premixed flames could be obtained at the very fuel lean condition by applying the stratified premixed flame concept.

진동하는 층류예혼합화염의 불안정성에 관한 연구

이원남(Wonnam Lee) 한국연소학회 2008 한국연소학회지 Vol.13 No.4

When a circular cylinder is placed at the center of a slot burner nozzle, once stable Woflhard-Parker type laminar lean premixed flame is changed to an oscillating flame with self-induced noise. The wrinkled flame surface showed the same pattern and frequency of the Karman vortex street at the downstream of a circluar cylinder. The interaction of flame with Karman vortex street is observed to be responsible for flame oscillation. The measured flame oscillation frequency is very similar to the estimated Karman vortex shedding frequency based on the St-Re relationship of the flow past circular cylinder, which could be considered as a strong evidence for the interaction between laminar pre-mixed flame and Karman vortex street. As Reynolds number increases oscillation frequency decreases and the self-induced noise level increases as well as the flame front is more severly wrinkled. This result suggests that the flame/vortex interaction becomes more active at higher Re.

충류화염 유동속도 측정을 위한 modulated Lll 기법

이원남(Wonnam Lee),이정수(Jung Soo Lee),남연우(Youn Woo Nam) 한국연소학회 2006 한국연소학회지 Vol.11 No.3

The modulated LII technique has been suggested for the measurement of axial velocity profiles of laminar diffusion flames. The theoretical background is explained based on the blackbody radiation and LII signal. Experimentally, soot particles in ethylene diffusion flames are heated by a modulated Ar-ion laser beam. LII signals and their phase angles are measured using a lock-in amplifier at the different flame heights and the axial flow velocities are obtained from the measured phase angle delay informations. The measured velocities are similar to those from LDV measurements under the same operating conditions. The effects of laser power, LII signal wavelength, and modulation frequencies are not sensitive to the velocity measurement. However, the choice of an optical chopper blade type could affect the measurement result. The use of a 6/5 chopper blade showed the better result that is possibly due to the square shape of modulated laser beam. This study successfully demonstrated that axial flow velocities of laminar diffusion flames can be measured by a new technique utilizing LII signal, which does not need particle seeding unlikely to LDV or PIV techniques.

Karman 와류 흘림과 층류 예혼합화염의 상호작용

이원남(Wonnam Lee),문두성(Dusung Moon) 한국연소학회 2008 KOSCOSYMPOSIUM논문집 Vol.- No.-

Flame oscillation and self-induced noise via interaction with a Karman vortex street have been investigated using a slot burner. The wrinkled flame surface showed the same pattern and frequency to those produced by Karman vortex street at the downstream of a circular cylinder. The measured flame oscillation frequency is very similar to the twice of estimated Karman vortex shedding frequency with Strouhal number of 0.2. This result could be a clear evidence of the interaction between laminar pre-mixed flame and a Karman vortex street. As Reynolds number increases with the increase of cylinder diameter from 1.67 ㎜ to 3.01 ㎜, the measured. oscillation frequency decreases from 334 ㎐ down to 175 ㎐ and the self-induced noise level increases from 64 ㏈ to 68 ㏈. The flame is more severely wrinkled with 3.01 ㎜ cylinder. The increased sound level and more severly wrinkled flame suggest that the flame/vortex interaction becomes more intense with the increase of Reynolds number.

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.

삼중화염 특성을 이용한 희박 예혼합 연소

이원남(Wonnam Lee),서동규(Dong-Kyu Seo),조승범(Seung-Beom Cho),선희석(Hee-Suk Sun),김기원(Ki-Won Kim),신연철(Yeon-Cheul Shin) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

The stabilization of fuel-lean laminar premixed flames with the triple flame configuration has been studied experimentally using a slot burner. The presence of fuel-rich flames significantly lowers the equivalence ratio limit for stable fuel-lean flames. The stable fuel-rich/lean combustion was obtained at the over-all equivalence ratio below 0.6. The increase of fuel flow rate in fuel-rich flames makes the fuel-lean flame more stable; however, the stability of fuel-lean flames was not sensitive to the equivalence ratio of a fuel-rich flame in the range of 1.3-2.4. The similar tendency on the stable fuel-lean combustion utilizing triple flame configuration was observed for both methane and propane flames, which indicates that the fuel-rich/lean combustion can be practical for the combustion systems using natural gas or LPG as fuel.

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.