空気流速の正弦波振動に対する伸長円筒状拡散火炎の応答

抄録

The response characteristics of a stretched cylindrical diffusion flame to oscillation of air flow was investigated experimentally. The cylindrical flame used in this study has a convex curvature with respect to air stream. The fuel used was methane, diluted with nitrogen, and the oxidizer is air. Oscillation frequency f was varied from 5 Hz to 250 Hz. Velocity at the outlet of air supplying nozzle was changed sinusoidally with four speakers. To evaluate a velocity gradient in oxidizer side from the flame front, the air velocity was measured using PIV. Flame radius, flame thickness and flame luminosity were obtained by high speed video camera. Results are summarized as follows: Fluctuation amplitude of the flame radius changes quasi-steadily in a low frequency range (5 Hz~25 Hz). The fluctuation amplitude decreases with increasing f when f is larger than 25 Hz. However, the response of flame luminosity is not quasi-steady at the low frequency range. Fluctuation amplitude of the flame luminosity has maximum value with respect to f, the maximum value is larger than that of a steady flame. The behavior of flame luminosity is different from that of flame radius.