Turbulent diffusion flames are inherently complex due to the coupling of highly nonlinearchemical kinetics and turbulence. In order to understand this interdependency oftransport and kinetic mechanisms, acoustically forced flames are useful because theyexhibit a larger range of combustion conditions than those observed in steady flames. Amathematical model was developed to simulate oscillating, counter flow diffusionflames. This model solves the unsteady conservation equations of mass, momentum,energy and species which are discretized using a non uniform grid. The structure of theresulting large DAE system is a tridiagonal block, because of spatial discretization.Most of the equations are devoted to the chemical species involved in the detailedkinetic scheme. The overall number of DAEs ranges between ~20,000 and ~30,000,depending on the number of grid points. The possibility of exploiting the tridiagonalblock structure is of crucial importance in drastically reducing CPU time. The solutionof the whole system of equations requires specific attention because of the numericalcomplexity, mainly related to the stiff nature of the kinetic mechanisms and to the hightemperature gradients. The flame behavior at extinction resulted more complex underunsteady conditions.
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