Numerical Modeling of Turbulent Premixed Flames in the Thin-Reaction-Zones Regime

Abstract

A new flamelet model has been developed for large-eddy simulation of turbulent premixed cornbustion in the thin-reaction-zones regime. In this regime of turbulent combustion, turbulent eddies smaller than the flame thickness exist and this small-scale turbulence disturbs the flame structure. Recent experimental observations show that turbulence interacts mostly with the chemically inert preheat zone while the thin reaction zone of the flame where all chemical processes occur remains unchanged. Therefore, flamelet models can be extended to this regime. The present model accounts for the different type of interactions between the flame and turbulence of different scales. The large-scale (larger than the flame thickness) turbulence increases the turbulent burning velocity by wrinkling the flame. On the other hand, the small-scale (smaller than the flame thickness) turbulence modifies the laminar flame propagation by enhancing the intensity of transport processes within the preheat zone. The developed model has been validated by carrying out a posteriori tests using a realistic gas turbine combustor problem. Comparisons with experimental data and conventional thin-flame model simulations show that the new model can significantly improve the predictions.