Mathematical Models of Premixed Flames

DMS 9803614

Mathematical Models of Premixed Flames, John K. Bechtold

This work proposes to systmatically derive generalized mathematical

models of premixed flame propagation through a variety of flow

conditions. Asymptotic methods will be employed to extract reduced

models from a complete set of equations governing combustion processes.

Of interest will be to account for flow conditions that are characteristic

of turbulent flows. Specific models will include the following phenomena:

unsteady flame structure, flow fields with concentration and thermal

gradients, and multi-component mixtures. These reduced models possess

a tremendous advantage over the full set of equations in that they

permit direct analysis of salient features characterizing practical

combustion systems. Therefore, it is further proposed that these new

models will be used to analyze simplified flame-flow configurations that

retain some of the essential features of turbulent reacting flows, including

unsteadiness and non-uniformities.

Most practical combustion systems, including internal combustion engines,

rocket engines and incinerators, operate in a turbulent regime. The study

of combustion in these environments provides valuable information on such

important issues as efficiency and emissions. These systems are very

complicated and are governed by huge sets of equations that are too large

to be solved even by the most sophisticated numerical techniques. Scientific

progress in these directions relies on the development of simplified

mathematical models; that is, reduced systems that retain the most essential

features of the combustion process, but that permit direct analysis. The

work proposed here involves the systematic derivation of flame models to

study flame propagation in a wide range of flow conditions, including

time-dependent and non-uniform flows. Of particular interest will be

to calculate burning rates and to identify conditions for which flames

will be extinguished.