Experimental study on the impact of swirl configurations and ammonia-methane blends on the ignition dynamics of a premixed annular combustor

This study presents a comprehensive experimental investigation into the ignition dynamics of a premixed annular combustor, focusing on the effects of swirl configurations and ammonia-methane blends on the light-round process. High-speed imaging from top and side views was utilized to examine flame propagation characteristics across a wide range of bulk velocities and equivalence ratios. Key findings indicate that variations in swirl configuration significantly affect the symmetry of flame front propagation and alter the burner-to-burner propagation mechanism. In swirl configurations, flame propagation is driven by both azimuthal motion and upstream movement, whereas non-swirling configurations rely primarily on azimuthal motion. Detailed flow diagnostics reveal that swirl intensity and swirler position redistribute axial and azimuthal velocity components, impacting light-round times. Moreover, ammonia-methane blends narrow the ignitable and stable combustion zones, increase the gap between ignition and extinction limits, and prolong light-round times. These effects are attributed to the lower reactivity of ammonia, characterized by lower flame speeds and longer ignition delay times. A significant linear correlation between flame propagation speed and the product of laminar flame speed and density ratio underscores their importance in the light-round process, independent of the fuel mixture type.