Abstract
When an accidental gas explosion occurs in an open space, a spherical flame outwardly propagates from the ignition point. The damage caused by the explosion depends strongly on the speed of the spherically expanding flame. In previous studies, empirical (or semi-empirical) models were proposed to estimate the flame speed. The goal of this study is to establish a theory that can predict flame speed without requiring empirical parameters. By reviewing previous theoretical studies, the critical flame radius at which flame acceleration initiates is identified as the key parameter, and it should be theoretically predicted to achieve the goal. In this paper, the linear stability theory developed by Zel'dovich et al. is compared with experimental data. The model prediction that the critical Peclet number is proportional to the Markstein number agrees qualitatively with previous experimental data. However, the theoretically predicted critical radius at which the perturbation amplitude increases more rapidly than the flame speed is smaller than the experimentally observed critical radius at which flame acceleration initiates, requiring further study.
