Numerical and experimental analysis of NO emissions from a lab-scale burner fed with hydrogen-enriched fuels and operating in MILD combustion

An experimental and computational investigation of a lab-scale burner, which can operate in both flame and MILD combustion conditions and is fed with methane and a methane/hydrogen mixture (hydrogen content of 60% by vol.), is carried out. The modelling results indicate the need of a proper turbulence/chemistry interaction treatment and rather detailed kinetic mechanisms to capture MILD combustion features, especially in presence of hydrogen. Despite these difficulties, Computational Fluid Dynamics results to be very useful, as for instance it allows evaluating the internal recirculation degree in the burner, a parameter which is otherwise difficult to be determined. Moreover the model helps interpreting experimental evidences: for instance the modelling results indicate that in presence of hydrogen the NNH and N₂O intermediate routes are the dominant formation pathways for the MILD combustion conditions investigated.