Reduced NO formation models for CFD simulations of MILD combustion

•Reduced kinetic schemes including thermal, N2O, NNH and HNO/NO2 intermediate routes.•Rate of production analysis in MILD combustion conditions.•Comparison with other schemes from literature and experimental NO.•Strong impact of NNH intermediate route.

Two reduced kinetic models, incorporating thermal, N2O, NNH as well as HNO/NO2 intermediate routes, are proposed for the quick evaluation of NO emissions from MILD combustion of H2-enriched fuels through post-processing of Computational Fluid Dynamics simulations. The models were derived from a Rate Of Production Analysis carried out with two different detailed kinetic schemes. The models were tested using data from the Adelaide Jet in Hot Coflow burner fed with CH4/H2 mixture and operated with three different O2 contents. Very satisfactory predictions of in-flame NO measurements were achieved for the three cases, indicating a good applicability of the models across a wide range of MILD combustion conditions. Significant impact of the NNH intermediate path was observed.