Asymptotic Analysis of Laminar Flame Propagation with Variable Transport Coefficients

Abstract

This paper reports an extended formula for the burning velocity of a steady onedimensional, planar, adiabatic flame in the case of a one-step irreversible decomposition reaction. As a generaliiation of previous analyses, which were concerned with constant-property flames, variable transport coefficients and variable mean molecular weight are taken into account. The resulting effects on the burning velocity are discussed and explained on physical grounds. A distinguished downstream zone involving a convective-reactive-diffusive balance is discovered to exist for all reaction orders greater than unity and to influence the burning rate if the Lewis number differs from unity, more strongly than the variable-property effects for reaction orders of three or greater.

Asymptotic Analysis of n-Heptane Ignition and Cool Flames with a Temperature-Explicit Model

“…The structure to be sought is one in which the upstream conduction occurs in a convective-diffusive zone, the main reaction occurs in a reactive-diffusive zone, and a convective-reactive zone is encountered downstream, where the temperature continues to increase but does so more slowly, the temperature always being presumed to be below 7^i n of Figure 1; (the hot flame can develop only when T > T m J. It will be found that a distinguished convective-reactive-diffusive transition region is needed between the main reaction zone of the cool flame and the convective-reactive region; distinguished zones of this type have been encountered in previous flame-structure analyses, for example in applications of activation-energy asymptotics to ordinary flames with reaction orders greater than unity (Rogg and Williams, 1985).…”