Combined Effect of Air Staging and Hydrogen Blending on Swirl Coupled Multi-Direct Jet Ammonia-Hydrogen Combustion Flow

This paper numerically investigates the coupled regulation mechanisms of the air staging ratio (RAS = 5%-20%) and hydrogen blending ratio (XH2 = 0%-20%) on combustion flow characteristics in a swirl coupled multi-direct jet ammonia-hydrogen combustor. The results demonstrate that three vortex structures are identified, including the main vortex ring, corner recirculation zone vortex ring, and sidewall jet counter-rotating vortex pair, with the corner recirculation zone serving as the high‑temperature flame-stabilizing core. Air staging enlarges the sidewall counter-rotating vortex pair, forms a primary zone with reduced oxygen concentration, lowers combustion temperature, and expands the medium‑temperature region. Hydrogen blending raises local temperature and flame height, while excessive blending promotes downstream ammonia transport. Air staging shifts the high‑temperature peak toward the center and relocates reactivity downstream, whereas hydrogen blending enhances OH concentration and significantly reduces NH2 level. NH2 mainly reduces NO at medium temperatures but forms NO at high temperatures. Air staging reduces outlet NO by up to 41.6% radially and 9.9% overall. Hydrogen blending cuts fuel-bound nitrogen and promotes NO reduction. At RAS = 20%, increasing the XH2 to 20% reduces outlet NO emissions by 15.38%.NH2