DIRECT NUMERICAL-SOLUTION OF TURBULENT NONPREMIXED COMBUSTION WITH MULTISTEP HYDROGEN-OXYGEN KINETICS

Results are reported from three-dimensional direct numerical simulatio ns of nonpremixed hydrogen-oxygen combustion using a reduced kinetic m echanism in low Mach number, decaying, variable density, isotropic tur bulence. The reduced chemical kinetics scheme is based on a seven-spec ies, ten-reaction hydrogen-oxygen mechanism. Realistic kinetic paramet ers were used. The speed of the entire chemical process was scaled rel ative to the mixing process by varying an appropriately chosen Damkohl er number. The simulation results were compared to predictions of the Conditional Moment Closure model. Next, predictions for the radical sp ecies concentrations based on steady-state and partial equilibrium ass umptions were compared to simulation results. A model is proposed whic h gives the thermochemical state as a function of the mixture fraction and a reaction progress variable. The thermochemical states are deriv ed and tabulated from homogeneous premixed calculations. The predictio ns of this model are compared to simulation data. An expression is der ived for the evolution of the error in a manifold approximation. (C) 1 997 by The Combustion Institute.