LES/PDF modeling of autoignition in a lifted turbulent flame: Analysis of flame sensitivity to differential diffusion and scalar mixing time-scale

摘要: Abstract The stabilization of lifted flames involves a complex competition between small-scale mixing and propagation flame kernels at the base flame. Here, effect species diffusivity on this process is explored. For purpose, large-eddy simulation (LES)/probability density function (PDF) methodology accounting for differential diffusion developed. A dynamic model scalar time-scale formulated to accurately describe turbulence-driven scalars small-scales. Autoignition-stabilized H2/N2 turbulent in vitiated coflow burner are chosen as test cases. Detailed chemical kinetics used along with situ adaptive tabulation (ISAT) accelerate computations. Four configuration cases considered: neglecting (Cases 1 2), considering (Case 3) but molecular transport H H2 4). appearing Cases 2, 3 4, which removes need specify value constant. It found that very sensitive diffusion. predictions major mass fractions, temperatures lift-off heights good agreement experimental data. Further, such could be achieved without changing any boundary conditions. In particular, increased upstream allows ignition survive dissipation, causing occur upstream. identified two critical play dominant role effect. also able capture change height temperature. results show even flames, zone can LES computations where significant part resolved, use enhanced LES/PDF/ISAT approach seen promising capturing physics accurately.