Species diffusion modeling in hydrogen flame–wall interaction

Flame–wall interaction (FWI) is critical to design safe, stable and low-emissions burners, and must be reassessed for next-generation hydrogen-fueled systems. Along all the physical processes, species transport highly affect quenching distance and thus wall heat flux. This study compares molecular- and Soret-diffusion formulations in one-dimensional laminar freely propagating flames and one-dimensional head-on quenching (HOQ) flames. Neglecting Soret diffusion leads to a 42% wall heat flux reduction for a stoichiometric flame at T u = 300 K and P = 1 atm. Including Soret diffusion reduces these discrepancies; however, a simplified Soret model still yields up to 5% wall-heat-flux error under lean conditions relative to multicomponent transport with its Soret diffusion. In contrast, varying the molecular-diffusion formulation has only a minor effect on the FWI quantities considered. Computational cost is also quantified: the full multicomponent formulation with Soret diffusion increases cost by 18% relative to a mixture-averaged model without Soret diffusion for a freely propagating H 2 flame. Finally, a grid-convergence study for HOQ (up to 512 points per flame thickness) shows that converging instantaneous heat release at quenching requires extremely fine meshes, which is unlikely to be feasible in LES. This study suggests that further experiments are needed to determine whether additional physical processes, such as surface reactions or water condensation under cold-wall conditions, could change this conclusion.