Flame and flow structure of premixed hydrogen/air combustion under different inlet flow rates

Abstract This study investigates premixed hydrogen/air combustion flow in a swirl coupling multi‐direct injection combustor, focusing on the effect of inlet flow rate distribution between direct and swirl flows on strain rate, NOx emission, and vortex structure. Results reveal that with the increase of the swirl flow rate, fluid centrifugal force strengthens, expanding the inner recirculation zone (IRZ) in intensity and range. The axial main vortex ring thickens (with higher surface roughness), a shear vortex forms near IRZ, wall counter‐rotating vortex pairs (CVP) intensify, and average vorticity rises significantly. Reaction rate improves notably, further amplified by intense mixing in the swirl‐direct jet shear zone. The flame front becomes shorter, the furthest axial distance of the flame front is reduced from 349 to 273 mm. Case 5 has an average strain rate of 597 s −1 , 31% higher than case 1. NOx emission rises from 3.0 to 3.25 ppm.