Large Eddy Simulations of a Turbulent Premixed Swirling Flame with Finite-Rate Chemistry and Flame-Wrinkling Turbulent Combustion Models

Abstract

Lean, premixed, swirl-stabilized flames are widely used in modern Dry Low Emissions gas turbine combustors; however, the turbulent combustion process under those conditions is known to be extremely sensitive and prone to instabilities. Numerical simulations can be a valuable tool in predicting the effects of alternative fuels; however, the sensitivity of the results to different models ought to be outlined. In this work, we present the results of Large Eddy Simulations performed on the CECOST burner with both Finite Rate Chemistry and Flamelet Progress Variable combustion models, non-adiabatic boundary conditions, and radiation modeling. The results highlight a surprising sensitivity of the simulation results in terms of mean fields, flame macrostructure, and flame dynamics. We discuss the model effects on the coupling mechanisms between turbulence and combustion, e.g., thermal expansion, and we conclude that, in particularly sensitive cases, they are capable of locally altering the flowfield to the extent it influences key flow structures on which flame stabilization relies. Additionally, the interaction between the smallest resolved scales of turbulence and the flame front is also affected, resulting in distinct flame dynamics.