抄録
This paper deals with the flame shape and fluctuation in the lean burn of methane-air mixtures. Cellular or planar flames formed on a flat burner are observed, and the gas temperature is measured with a Pt/Pt-13%Rh thermocouple to find out the flame shape. When the equivalence ratio is higher than 0.74,planar flames are formed; cellular flames appear at lower equivalence ratios. As the equivalence ratio becomes lower, the cell size and cell depth are increased. The diffusive-thermal effect plays an important role in the appearance and characteristics of cellular flames. We also measure the fluctuation of brightness of premixed flames and obtain the power spectrum density of the brightness fluctuation. At low frequency range (f<0.035Hz), the power spectrum density is almost constant, i. e., the white noise is observed. At high frequency range, on the other hand, the 1/f^<3.5> spectrum is observed. In addition, the power spectrum density has a peak at high frequency range, under the condition that cellular flames appear.
