Filtered Wrinkled Flamelets model for Large-Eddy Simulation of turbulent premixed combustion

Abstract

Models for combustion LES based on a geometrical description of the reactive layer are well suited to capture the turbulent flame front displacement speed, but do not predict the filtered chemical flame structure. This article aims to discuss and model the impact of the flame sub-filter wrinkling level on the species production, with a focus on carbon monoxide emission. For that purpose, 2-D wrinkled flames with a sinusoidal pattern, which include detailed chemistry effects, are manufactured. Three controlling parameters are identified: the flame filter size, the sub-filter flame wrinkling and the number of flame patterns contained within the sub-filter volume. This new flame archetype, named Filtered Wrinkled Flamelets (FWF), may be embedded in various combustion modeling frameworks. In the present paper, it is used to build-up a filtered chemical look-up table in order to model the unclosed terms of the filtered progress variable equation. A priori tests are conducted by analyzing an existing turbulent premixed flame database. A posteriori tests consist in modeling the swirling bluff-body stabilized Cambridge flame. Results analysis shows that accounting for sub-filter flame wrinkling on the chemical flame structure is mandatory to predict intermediate species such as CO.