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The Influence of Stretch on a Premixed Flame With Two-Step Kinetics

1983; Taylor & Francis; Volume: 33; Issue: 1-4 Linguagem: Inglês

10.1080/00102208308923667

1563-521X

K. Seshadri, Norbert Peters,

Fire dynamics and safety research

Abstract The structure of a steady, planar. premixed flame in a slowly expanding gas flow is analyzed. The reaction kinetics are represented by a mechanism consisting of a chain branching reaction and a chain breaking reaction. An asymptotic analysis is performed in the limit of a large value for the activation energy of the chain branching reaction, with the activation energy for the chain breaking reaction presumed to be zero. The analysis is valid for cases where the mass fraction of the intermediate species is of order unity, An analytical expression is obtained for the change of the mass burning rate with the Karlovitz number, the parameter characterizing flame stretch. This expression shows the role of differential diffusion of heat and the reactant, of differential diffusion of reactant and intermediate species and of enhanced diffusion of intermediates on flame propagation. It is seen that these three different effects may cancel each other. Depending on the parameter range the mass burning rate may be either decreased or increased.