Two-Dimensional Observation of Fluctuation in Methane-Air/LPG-Air Premixed Flames by Planar Laser Induced Fluorescence (PLIF)

Abstract

OH-PLIF images were observed sequentially at a rate of 30 frames/s on CH4-air and liquefied petroleum gas (LPG)-air premixed flames, followed by statistical analysis including Fast Fourier Transformation (FFT) to examine flame fluctuations at inner and outer regions of the premixed flames. Characteristics in the FFT power spectra were different between the inner and outer cases due to a difference in mixing condition of the fuel gas and air between the inner and outer flame regions. Correlation profiles between average value and standard deviation of the consecutively measured OH-PLIF intensity showed that combustion reaction activity was not always a prevailing driving force for the fluctuation. This characteristic was independent of the difference in mixing condition of the fuel gas and air between the inner and outer flame regions. Key words: flame fluctuation, premixed flames, OH-PLIF distribution, statistical analysis