Investigation into the Effect of H2-Enriched Conditions on the Structure and Stability of Flames in a Low-Swirl Combustor Derived from Aero-Engine Design

This study introduces an innovative approach involving the injection of hydrogen into a low-swirl, non-premixed flame, which operates with gaseous fuels derived from an air-blast atomizer designed for aero-engine applications. The aim is to characterize how hydrogen enrichment influences flame structures while maintaining a constant thermal output of 4.6 kW. Using high-speed chemiluminescence imaging, three fueling conditions were compared: the first involved pure methane/air, while the second and third conditions introduced varying levels of hydrogen to an air-methane mixture. The results reveal significant effects of hydrogen enrichment on flame characteristics, including a slightly shorter length and a wider angle attributed to heightened expansion within the Combustion Recirculation Zone. Moreover, the emission of UV light underwent considerable changes, resulting in a shifted luminosity zone and reduced variance. To delve deeper into the underlying mechanisms, the researchers employed Proper Orthogonal Decomposition (POD) and Spectral Proper Orthogonal Decomposition (SPOD) analyses, showing coherent structures and energetic modes within the flames. Hydrogen enrichment led to the development of smaller structures near the nozzle exit, accompanied by longitudinal oscillations and vortex shedding phenomena. These findings contribute to an advanced understanding of hydrogen's impact on flame characteristics, thereby propelling efforts toward improved flame stability. Additionally, these insights hold significance in the exploration of hydrogen as an alternative energy source with potential environmental benefits.