High-Fidelity Large Eddy Simulation of a Lifted Hydrogen-Air Flame in a Dual-Swirl Coaxial Injector

Hydrogen is a promising low-emission fuel for next-generation combustion systems, yet its high flame speed and wide flammability range introduce significant challenges for flame stabilization and NOₓ mitigation. This study presents high-fidelity Large Eddy Simulations (LES) of Flame L, a lifted, partially premixed hydrogen–air flame formed in a dual-swirl coaxial injector from the HYdrogen LOw NOx (HYLON) program. The simulations incorporate detailed H₂/NOₓ chemistry, adaptive mesh refinement, and experimentally matched inflow conditions to resolve the coupled effects of flow dynamics, scalar mixing, and chemical kinetics. Validation against experimental measurements of velocity and temperature demonstrates that the LES accurately reproduces the dual-jet structure, central recirculation zone, and key turbulence characteristics associated with the lifted flame regime. Analysis of the reactive flow field reveals that the flame stabilizes along the stoichiometric surface and the inner recirculation zone, consistent with triple-flame–type stabilization mechanisms. The results provide detailed insight into the underlying flame–turbulence interactions, mixed premixed/diffusion burning modes, and heat-release behavior, contributing to the development of more stable and low-NOₓ hydrogen combustion technologies.