Modeling of graphite oxidation in a stagnation-point flow field using detailed homogeneous and semiglobal heterogeneous mechanisms with comparisons to experiments

Numerical simulation results are presented on the mass burning rate and the gas-phase flame structure of a heated cylindrical graphite rod in a stagnation-point flow field, using detailed homogeneous chemical kinetics and semiglobal heterogeneous chemical kinetics. Extensive comparisons with new experimental data and data from the literature are shown for various oxidizer compositions, pressures and strain rates. The relative importance of the carbon-radical reactions in the two semiglobal heterogeneous mechanisms employed is demonstrated, while the deficiencies and limitations of applying semiglobal heterogeneous mechanisms for graphite rod oxidations are identified. Under simplifying assumptions, a method for including the graphite porosity in the present quasi-one dimensional formulation is described. The need to develop elementary reaction mechanisms for the heterogeneous kinetics and the importance of accurate estimation of effective surface area is stressed.