PDF modeling of CO and NO formation in lean premixed methane flames

In this paper, CO and NO formation in a premixed turbulent methane flame is simulated with a stochastic model of combustion. The model proposed is a combination of both the computational fluid dynamics and the Monte Carlo methods for the solution of the joint probability density function. Finite chemical kinetics is represented by a GRI-derived reduced-chemistry model. This resultant model is used to simulate a lean, premixed, bluff-body, stabilized flame for which experimental data are available. Under this condition, the prediction of NO formation is a challenge because of its low concentrations (typically a few parts per million) and because every NO-formation route is relevant. The model used for the molecular mixing includes a variable mixing time, covering the range from the Kolmogorov scale to the integral scale. A lookup table is used to estimate the thermochemical properties and is found to be more adequate than direct integration. The results are compared with an experimental database.