Influence of the Turbulent Damköhler 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 adiabatic wall. A flamelet model along with a low Reynolds number κtilde;-ϵtilde; model are used to close the set of the Favre averaged relevant equations written in an axisymmetrical co-ordinate system. A finite differences program based on the method of artificial compressibility is used to solve the system of equations. The effects of the turbulent Damköhler number D T on the flow structure are examined. 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 Damköhler 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 analysis on the symmetry axis puts into evidence the influence of D T on the production of the turbulent kinetic energy and the limit of the gradient assumption for the scalar turbulent fluxes.