J054013 球状伝播予混合乱流火炎の火炎面形状の幾何学的特性

Abstract

Turbulent burning velocity of spherically propagating premixed turbulent flame keeps increasing during flame propagation. The flame front area is considered to be the most dominant factor to turbulent burning velocity. Thus, it is important to evaluate the flame front area during flame propagation in order to clarify the variation of turbulent burning velocity with flame propagation. However, to evaluate the turbulent flame front area quantitatively is generally difficult because of the convoluted structure of turbulent flame front. The fractal analysis is one of the techniques to deal with the convoluted figures. In this study, the fractal analysis was conducted for stoichiometric spherically propagating premixed turbulent iso-octane/air flames. The laser tomograph technique was adopted to obtain the cross-sectional images of turbulent flames. The fractal characteristics, such as fractal dimension, inner-cutoff and outer-cutoff scales, were obtained. Then, the correlation (ε_o/ε_i)^<D_3-2> (1-KaMa) of turbulent burning velocity was investigated. Here, ε_o, ε_i,D_3, Ka and Ma are outer-cutoff scale, inner-cutoff scale, fractal dimension, turbulence Karlovitz number and Markstein number, respectively. The correlation (ε_o/ε_i)^<D_3-2> (1-KaMa) of turbulent burning velocity was well related to the measured value of turbulent burning velocity in the examined conditions of this study