Effect of Flame–Wall Interaction on Blending Flame Characteristics in Ammonia and Methane Cofiring

Ammonia/methane cofiring is one of the effective solutions to low laminar burning velocity and flame instability for the industrial application of ammonia energy, where the wall limitation in the combustion chamber can affect flame behavior. The effect of flame–wall interaction (FWI) on ammonia/methane flames considering both the wall distance and ammonia blending ratio is investigated in this study. The impinging blended flame behavior is discussed using experiments and large eddy Simulation. Results indicate a distinct transition in flame luminosity from high-intensity to low-intensity regions as the ammonia blending ratio increases. Both experimental results and numerical simulations reveal that FWI significantly impacts flame behavior, manifesting as local jet flame quenching predominantly at H/D=55 wall distance (H being the distance and D the nozzle diameter) and wall quenching strengthened at H/D=75. Notably, the global quenching phenomenon is minimized at H/D=65, attributed to a balance between convective and diffusion instabilities, resulting in a lower temperature gradient and a significantly higher heat release rate. Specifically, at 20% ammonia blended ratios and H/D=65, continuous vortex structures promote effective fuel–air mixing and combustion, leading to a widely distributed high-value area of wall heat flux and its peak value. It can be attributed to the coupling effect of ammonia blending and the local quenching behavior of jet flame and wall quenching behavior from FWI in the blending jet impinging flame.