Application of the Coherent Flamelet Model to Counterflow Turbulent Premixed Combustion and Extinction

The Coherent Flamelet Model (CFM) is applied to symmetric counterflow turbulent premixed flames of Kostiuk et al. (1993b). The flame source term is set proportional to the sum of the mean and turbulent rate of strain while flame quenching is modeled by an additional multiplication factor to the flame source term. The turbulent rate of strain is set proportional to the turbulent intensity to match the correlation for the turbulent burning velocity by Abdel-Gayed et al. (1987). Mixing with ambient air is assumed to be proportional to the mass fraction of the burned and unburned mixture in each computational cell. The predicted flame position and turbulent flow field coincide well with the experimental observations. The nozzle exit velocity at extinction shows qualitative agreement for variation of the equivalence ratio, nozzle separation distance and exit turbulence condition.