Large Eddy Simulation of a Turbulent Lifted Flame using Conditional Moment Closure and Rate-Controlled Constrained Equilibrium

The objective of this paper is the simulation of a turbulent flame by employing the Rate-Controlled Constrained Equilibrium (RCCE) approach for the chemistry reduction, and Large-Eddy Simulation (LES) coupled with Conditional Moment Closure (CMC) for the turbulence-chemistry interaction modelling. RCCE is a systematic method for mechanism reduction, based on the concept that certain species characterized by faster time scales are in a constrained equilibrium state, determined by the concentration of the species controlled by the chemical kinetics. A general system of differential equations can be derived, independent on the selection of the fast and slow species (which appears as a parameter). The RCCE system is used to compute the conditional source term in the CMC equation. The flame simulated here is a methane flame issuing into a vitiated co-flow formed by hot combustion products, the "Cabra" flame, which is controlled by auto-ignition and is therefore sensitive to the chemical mechanism. The results show an influence of the chosen chemistry in the ignition length.