Modelling nitrogen oxide emissions in turbulent flames with air dilution: Application to LES of a non-premixed jet-flame

The aeronautical industry faces the challenge of designing new engines with a better specific fuel consumption while decreasing pollutant emissions such as nitrogen oxide (NO). To this aim, many Computational Fluid Dynamics (CFD) models have been developed to predict NO emissions. Most of these models are based on a simplified description of the nitrogen chemistry, while few of them attempt to take into account the whole NO chemistry and its interactions with carbon oxidation. This article presents a new model, called NOMANI (Nitrogen Oxide emission model with one-dimensional MANIfold), which predicts NO emissions from all chemical processes present in detailed mechanisms and which is well suited to aeronautical burners. To have a good estimation of the NO mass fraction produced in the flame front and in the burnt gases, two progress variables are used. The first one is built from major carbon species, and once carbon chemistry is completed the NO mass fraction is used as a second progress variable with possibility of accounting for dilution by secondary air. This modeling is first assessed thanks to a phenomenological study based on the nitrogen chemistry under dilution by fresh air. The model is then applied and validated in highly resolved Large-Eddy Simulations (LES) of the TNF Sandia Flame D.