Dependence of Surface Flash Velocity on the Density and Thickness of Napped Layer

Abstract

The previously proposed model for the surface-flash phenomenon is modified to account for the influence of nap thickness and the dependence of reaction rate on fuel concentration. As before, the model is an extension of ordinary premixed-flame theory and considers heat loss to the surrounding environment and fiber pyrolysis. The activation-energy-asymptotics technique is applied to obtain an asymptotic analytical solution of the model. The model predicts the existence of the critical nap thickness and the critical nap density for the occurrence of surface flash. It also shows that the surface flash velocity significantly depends on the nap density but only weakly on the nap thickness. These theoretical results qualitatively agree with previous experimental observations.