Simulations of the coupling between combustion and radiation in a turbulent line fire using an unsteady flamelet model

Abstract

The general objective of this study is to evaluate the potential of advanced combustion and radiation models for large eddy simulations (LES) of fires. We adopt here an unsteady laminar flamelet model that includes: detailed information on combustion chemistry through a tabulated chemistry approach; a careful description of the combustion-radiation coupling (local radiation phenomena are treated by the flamelet solver while non-local radiation phenomena are treated by the LES solver through the radiative transfer equation); a description of subgrid-scale turbulence-radiation interactions; and a description of non-grey radiation effects (through a Weighted-Sum-of-Grey-Gases – WSGG model). The new flamelet-based combustion/radiation model is incorporated into the LES solver FireFOAM and is evaluated by comparisons with experimental data obtained in a turbulent line burner experiment previously studied at the University of Maryland. Comparisons between simulated and measured temperatures show relatively good agreement (and significant improvements compared to our previous work). In addition, comparisons between simulated and measured values of the global radiant fraction show that provided that the WSGG option is used, the flamelet model is capable of simulating changes in the flame radiative emissions that result from changes in the oxygen strength of the coflow.