Toward finite-rate chemistry large-eddy simulations of sooting swirl flames

Abstract

ABSTRACTThis paper presents time-resolved numerical simulations of a well-characterized sooting swirl flame at elevated pressure. Recently published unsteady Reynolds averaged Navier–Stokes simulations (URANS) are compared here to newly performed large eddy simulations (LES). Finite-rate chemistry, where transport equations are solved for each chemical species, is employed for the gas phase, a sectional approach for polycyclic aromatic hydrocarbons (PAHs), and a two-equation model for soot particles. Feedback effects such as the consumption of gaseous soot precursors by growth of soot and PAHs are inherently captured accurately by a coupled solution of the set of governing equations. The numerical results (velocity components, temperature, and soot volume fraction) compare well with experimental data. No significant differences between URANS and LES are observed for time-averaged temperatures and velocity components, while the prediction of soot is significantly improved by LES. It will be shown that an accurate description of the instantaneous flame structure (especially of the hydroxyl radical distribution) by resolution of turbulent scales is of fundamental importance for accurate soot predictions in confined swirl flames with strong secondary air injection.