On no formation in turbulent diffusion flames

A theoretical and experimental study on NO formation in turbulent diffusion flames is presented. Detailed in-flame measurements for both major species and nitrogen oxides concentrations have been performed and have been compared with 2-D numerical calculations. From this comparison, it is concluded that (i) the prompt NO mechanism is the dominant route for NO formation and (ii) the reactions between NO and hydrocarbon radicals, recycling NO back into fuel-NO reactions, play an important role in the global reduction of NO. Post-flame measurements next confirm that NO emission indices are proportional to the jet Froude number. The numerically calculated values of these indices, according the model used, present a good agreement with the experimental data and are found to be proportional to the residence time of the reaction products in the high-temperature reaction zone.