Effect of Flame Inherent Instabilities and Turbulence on Flame Structural Characteristics

Abstract

To evaluate the effect of turbulence and inherent instabilities of flame on flame structural characteristics, experiments were conducted with a 70%-H2/30%-CO premixed flame at various equivalence ratios and turbulence intensities at atmospheric pressure and temperature. The convex and concave regions of the large-scale wrinkle in the flame front were extracted and quantitatively evaluated; wavelet transform was used to decompose disturbances in the flame front. The results show that with the development of the flame, the flame became unstable, the fluctuation range of the pulsating radius increased, the area and area ratio of the convex regions increased, and the average area and uniform degree of the convex and concave regions increased. As the turbulence intensity increased, the area and area ratio of the convex regions increased, the average area and uniform degree increased, and the disturbance energy at the same scale increased. Large-scale disturbances were the main factor affecting the flame’s structural characteristics. With the increase in equivalence ratio, the effect of thermal-diffusive instability and turbulence on flame structural characteristics was reduced, decreasing the fluctuation range of the pulsation radius. The interaction between disturbances of different scales in the flame front resulted in the uneven distribution of the pulsation radius.