Ammonia-methane combustion in a swirl burner: Experimental analysis and numerical modeling with Flamelet Generated Manifold model

Ammonia/methane flames gained significant attention since this is a probable step toward a sustainable, carbonfree economy in the near future. Therefore, three such flames were numerically and experimentally investigated in a swirl burner, focusing on robust modeling methods to facilitate the spreading of ammonia combustion in the industry. Chemistry was considered by the mechanism of Okafor and employed through the Flamelet Generated Manifold model. Both Particle Image Velocimetry and OH* measurements confirmed the appropriateness of the numerical model in all cases. It was demonstrated that the modeling approaches are applicable at both near stoichiometric conditions and close to the flammability limit of ammonia. The comparison of steady-state and the mean unsteady results implied that the steady calculations are appropriate only for the chemical conversion and fall behind in flow field modeling. The Root Mean Square velocity was identical up to the reaction zone for all cases, while its value decreased with the increase of ammonia concentration. The CO emission matched underpredicted experiments by a magnitude; however, the concentration was very low. Regarding the NOx emission, the CFD underpredicted it by a factor of two.