초록 열기/닫기 버튼
하향 전파하는 예The effects of Lewis number on acoustic instability of downward propagating flames in a tube were studied experimentally. The discussion first treated the coupling effects between cellular, Darrieus-Landau and primary acoustic instabilities in non-equidiffusive flames. Low Lewis number tended to generate stronger primary acoustic sound and to suppress cellular instability under the fixed laminar burning velocity. Also, displacement flame velocities declined with low Lewis number because of diminished flame surface area with absence of combustion instability. We then described the effects of Lewis number on secondary acoustic instability. To generate secondary acoustic instability at desired time, we adopted the CO2 laser irradiation method to alter the shape of the flame front. The results showed that for a Lewis number below (above) unity, relatively stronger (weaker) acoustic sound is produced under the same laminar burning velocity, because the combustion wave becomes sensitive (insensitive) to pressure fluctuations in the acoustic field due to curvature effects. Therefore, shorter (longer) transition time was required from secondary acoustic instability to turbulent motion.혼합 화염에서 루이스 수에 따른열음향 불안정성의 동적거동 변화
Dynamic Behaviors of Acoustic Instability According to Lewis Number in Downward-PropagatingThe effects of Lewis number on acoustic instability of downward propagating flames in a tube were studied experimentally. The discussion first treated the coupling effects between cellular, Darrieus-Landau and primary acoustic instabilities in non-equidiffusive flames. Low Lewis number tended to generate stronger primary acoustic sound and to suppress cellular instability under the fixed laminar burning velocity. Also, displacement flame velocities declined with low Lewis number because of diminished flame surface area with absence of combustion instability. We then described the effects of Lewis number on secondary acoustic instability. To generate secondary acoustic instability at desired time, we adopted the CO2 laser irradiation method to alter the shape of the flame front. The results showed that for a Lewis number below (above) unity, relatively stronger (weaker) acoustic sound is produced under the same laminar burning velocity, because the combustion wave becomes sensitive (insensitive) to pressure fluctuations in the acoustic field due to curvature effects. Therefore, shorter (longer) transition time was required from secondary acoustic instability to turbulent motion. Premixed Flames
