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Show the production term of the transport equation of the temperature variance equals the dissipation term. The proposed model is used to simulate the NO emissions in several natural gas-oxygen flames. A water-cooled furnace and a refractory-lined furnace are fired with different momentum burners, at rates between 0.8 and 1.0 M W . The experimental results are compared to several N O emission models, namely the AL model, Fluent model, and PW model respectively. The results show that the AL model accurately predicts the N O emissions in the flue gases when compared to the experimental data in all the investigated cases. The comparison between experimental measurements and the different numerical simulations shows significant improvements of the AL model. These results are attributed to the more realistic hypothesis in modelling the N O emissions into the flame. The study concludes that further improvements in the combustion models of turbulent diffusion flames are necessary for a better understanding and more accurate prediction of the N O emissions. At the same time, this study shows the necessity to continually improve the present N O models, in the sense of more accurate descriptions of flame fluctuations, and the introduction of non-equilibrium effects. ACKNOWLEDGMENTS Data from Refs. 1 and 17 has been extracted form a work financed by OXYFLAM, a research consortium including IFRF, AGA, Air Liquide, Gaz de France, Hoogovens, Linde, Nippon Sanso and Tokyo Gas. 21 |