Can We Predict the Occurrence of Surface Flash?

Abstract

Surface flash over a napped fabric is theoretically investigated. A mathematical model is presented to predict the surface flash velocity as a function of nap density, a governing parameter of the phenomenon. The model is an extension of a premixed-gas theory and considers the pyrolysis of fibers and the heat loss to the surroundings. The activation energy asymptotics (AEA) technique is applied to obtain an analytical solution of the model. The model solution correctly reproduced the following two important experimental observations:(1) the dependence of surface flash velocity on the nap density, that is, V₀ ∼ ρ_n⁰ for small ρ_n , and V₀ ∼ ρ_n^-1 for large ρ_n , where V₀ is the surface flash velocity and ρ_n the nap density ; (2) the existence of the critical nap density above which surface flash does not occur.