An experimental investigation on self-acceleration of cellular spherical flames

The cells that continuously develop over the flame surface of an expanding spherical flame increase its area and thereby the global propagation rate, resulting in the possibility of self-acceleration. The present study examines whether this self-acceleration could be self-similar, and, if so, whether it could also be self-turbulizing. Extensive experiments at elevated pressures and thereby reduced laminar flame thicknesses and enhanced propensity to exhibit Darrieus-Landau instability were conducted for hydrogen/air mixtures over an extensive range of equivalence ratios. The results demonstrate the strong possibility of self-similar flame acceleration, weak influence of the system pressure and diffusional-thermal instability, and a corresponding moderate spread in the power-law acceleration exponent.