INFLUENCE OF THE TURBULENT DAMKOHLER NUMBER ON THE STRUCTURE OF PREMIXED FLAMES IN A STAGNATION FLOW

Results are reported from a numerical analysis of a premixed turbulent flame stabilized in a stagnating reactant stream impinging on an adia batic wall. A flamelet model along with a low Reynolds number (k) over tilde-<(epsilon)over tilde> model are used to close the set of the Fa vre averaged relevant equations written in an axisymmetrical co-ordina te system. A finite differences program based on the method of artific ial compressibility is used to solve the system of equations,The effec ts of the turbulent Damkohler number D-T on the flow structure are exa mined. It is shown that the position of the flame (with respect to the wall) and its shape (closed or open flame brush) strongly depend on D -T. The value of the turbulent Damkohler number that corresponds to an open flame brush (only reactants are present at the stagnation point) is found to be comparable to the one obtained in the literature by an asymptotic analysis of the flow on the symmetry axis. A detailed anal ysis on the symmetry axis puts into evidence the influence of D-T on t he production of the turbulent kinetic energy and the limit of the gra dient assumption for the scalar turbulent fluxes.