Large eddy simulation of a piloted turbulent jet flame

In this paper, Large Eddy Simulations (LES) have been performed on an ethylene/air piloted turbulent sooting jet flame to examine the importance of chemistry-turbulence interaction. The current work focuses on the effects of turbulent transport on the formation of Polycyclic Aromatic Hydrocarbons (PAH). These species are of primary importance since their concentrations control directly the soot nucleation rates. The Flamelet/Progress Variable (FPV) approach is adopted to describe the combustion of all gas phase species except for PAH. Radiative heat transfer is considered by introducing enthalpy defect as an additional parameter in the FPV model. This parameter represents a measure of the departure from the non-radiating flamelet solutions. The FPV model accounting for radiative heat losses is closed in the current LES using a presumed subfilter Probability Density Function (PDF) approach. Given the large time scale related to PAH formation, PAH species exhibit large unsteady effects. To model these effects, transport equations are solved for these species. The chemical source terms are closed using a recently developed linear relaxation model. The importance of the interactions between turbulence and PAH chemistry is highlighted by comparing the PAH yield resulting from the LES to steady state flamelet predictions.