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Finite-Rate Diffusion-Controlled Reaction in a Vortex.


pdf icon Finite-Rate Diffusion-Controlled Reaction in a Vortex. (1156 K)
Rehm, R. G.; Baum, H. R.; Tang, H. C.; Lozier, D. C.

Combustion Science and Technology, Vol. 91, No. 1-3, 143-161, 1993.

Keywords:

flame fronts; formulations; equations; diffusion flames; bimolecular reactions

Abstract:

The influence of a vortex on a gaseous diffusion reaction is examined. The vortex is taken to be two dimensional, and the species are initially assumed to occupy adjacent half spaces. In the flame-sheet limit, thermal expansion and the effects of variable diffusion are taken into account. A global similarity solution exists for this problem, and a simple expression for the solution is determined in the asymptotic limit of large Schmidt number. The problem is also analyzed for finite-rate chemistry, appropriate for an isothermal, bimolecular reaction. The problem depends upon three parameters, Reynolds number, Schmidt number and the equivalence ratio, with the Damkohler number equal to the dimensionless time. The structure of the reaction region normal to the flame front is examined as a function of time. The evolution of the reaction to a state relation, dependent only upon the mixture-fraction variable, is demonstrated as the Damkohler number becomes large.