Modelling Turbulent Premixed Flames using Multiple Mapping Conditioning

Abstract

A turbulent-chemistry interaction model with shadow-position reference variables developed in the MMC framework is presented and analysed. This model controls flame propagation using an external parameter λ that represents the ratio of the reference propagation speed to the laminar flame speed. Results demonstrate that the model effectively localises the mixing in the shadow-position space, and since the shadow and physical positions of the notional particles follow each other, mixing localisation in the shadow-position reference space results in the preservation of the flamelet-like inner structure of flames and the prevention of excessive unphysical mixing across the flame front in the physical space. The assessment of the model's performance with constant global parameters for flames in the thin reaction zones regime shows substantial sensitivity of the model's performance to variations in the λ parameter. Therefore, it is concluded that the λ parameter should be determined locally based on the local length and velocity scales of the flow and the LES grid size. It has been shown that when the λ parameter is evaluated locally, and reaction-induced micromixing augmentation effects are calculated based on the sub-grid scale wrinkling factor, the model can accurately estimate the resolved propagation speed. The comparison of the numerical results and experimental data demonstrates good agreement with experimental data for major species. Minor species' production and consumption rates' prediction can be improved by incorporating a detailed chemical mechanism. Analysis of the model for flames nominally located in the broken reaction zones shows that the flow-adapted model overestimates reaction rates for flames with very high Karlovitz numbers, and it is required to investigate if the consideration of reaction-induced micromixing enhancement effects should be conditioned on local Karlovitz and Damköhler numbers.