Investigation of NH 3 /CH 4 Flame Structure and Dynamics in a Swirl Turbulent Non-Premixed Burner

The urgent need for renewable energy has positioned ammonia (NH3) as a promising carbon-free energy carrier due to its ease of transport and high energy density. However, its use is hindered by low flame velocity, high NOx emissions, low calorific value, and combustion instability. Blending ammonia with methane (CH4), a renewable fuel derived from biomass, can improve reactivity and improve flame stability. This study investigates the mechanisms of flame stabilization in non-premixed swirling flames fueled by NH3/CH4 mixtures. Experiments were conducted in a combustion chamber equipped with a turbulent swirl burner featuring radial fuel injection through eight equally spaced ports. The swirl number is set at 0.8, and tests were performed using methane as a reference and NH3/CH4 blends with varying volumetric ratios (50/50, 60/40, and 90/10%), under both constant total flow rates and constant flame power conditions. Flame structure and behavior were analyzed using OH* and NH2* chemiluminescence imaging, while the flow field was characterized using Laser Doppler Anemometry (LDA). Emissions of NO and NO2 were also quantified from dry exhaust gases using multi-gas analyzers. The results reveal that fuel composition and operating conditions significantly influence flame dynamics, including the stabilization zone, flame shape, and liftoff height. Increasing the ammonia content notably affects the velocity distribution, expands zones of negative velocity, and decreases liftoff heights, highlighting the impact of ammonia’s lower flame propagation velocity. These findings underscore the interplay between flow dynamics and fuel composition, providing key insights for optimizing ammonia-methane combustion systems under various operating conditions.