Impact of direct integration of Analytically Reduced Chemistry in LES of a sooting swirled non-premixed combustor

Large-eddy simulation (LES) of a swirl-stabilized non-premixed ethylene/air aero-engine combustor experimentally studied at DLR is performed, with direct integration of Analytically Reduced Chemistry (ARC). Combined with the Dynamic Thickened Flame model (DTFLES), the ARC-LES approach does not require specific flame modeling assumptions and naturally adapts to any flow or geometrical complexity. To demonstrate the added value of the ARC methodology for the prediction of flame structures in various combustion regimes, including formation of intermediate species and pollutants, it is compared to a standard tabulation method (FPI). Comparisons with available measurements show an overall good agreement with both chemistry approaches, for the velocity and temperature fields. However, the flame structure is shown to be much improved by the inclusion of explicitly resolved chemistry with ARC. In particular, the ability of ARC to respond to strain and curvature, and to intrinsically contain CO/O2 chemistry greatly influences the flame shape and position, as well as important species production and consumption throughout the combustion chamber. Additionally, since both chemistry descriptions are able to account for intermediate species such as OH and C2H2, soot formation is also investigated using a two-equations empirical soot model with C2H2 as the sole precursor. It is found that, in the present configuration, this precursor is strongly impacted by differential diffusion and partial premixing, not included in the FPI approach. This leads to a strong under-prediction of soot levels by about one order of magnitude with FPI, while ARC recovers the correct measured soot concentrations.