• Pollutant emissions
• NOx
• Numerical model
• CFD
• MILD combustion
• JHC burner
• Pilote-scale burner

The work is focused on the development of comprehensive models for NOx formation in systems operating in MILD combustion (also known as flameless combustion). Such novel technology is based on a flame dilution, achieved through recirculation of combustion products in the reaction region. MILD combustion ensures high combustion efficiency with low NOx emissions and it is promising for low-calorific fuels, industrial wastes as well as in presence of H2.
Because of the low temperature conditions, the thermal NO formation becomes less significant; hence other routes, such as N2O/NO and NNH route should be taken into account. The latter could be important in presence of H2.
The present thesis is motivated by the need to revise existing NO models to be incorporated in CFD tools for conditions typical of MILD combustion.
A new reduced NO model (including thermal, prompt, N2O and NNH pathways) is derived and tested for a Jet in Hot Coflow burner fed with CH4/H2, fully characterised in literature and emulating MILD combustion.
Subsequently, another model is derived and applied to a NG-fired pilot-scale burner, whose experiments were performed by also injecting an ammonia solution. Large attention is paid also to the development of the burner CFD model.