Flame Spread over a Combustible Solid

Abstract

This paper reviews a part of studies on flame spread over a combustible solid with a focus on modeling approaches to the phenomenon. By reviewing the de Ris theory and a simplified version of it, it is first discussed that the spread rate is an eigenvalue, and its determination requires an eigenvalue relationship. Smoldering propagation without flame is also discussed. When smoldering propagation occurs because of limited oxygen supply, fingering instability often appears. The mechanism of fingering instability is similar to that of diffusive-thermal instability of gaseous premixed combustion, and therefore the Lewis number is a key parameter. Considering smoldering propagation in a narrow space, the definition of an effective Lewis number of smoldering propagation is proposed, and the results of numerical simulations and experiments are compared at two different effective Lewis numbers.