Numerical study of the effect of wall thermal conditions and oxidant structure on the flame structure and combustion regime in non-premixed combustion furnace

The aim of this study is to investigate the effect of wall thermal conditions and oxidant composition on the flame structure and map of combustion regimes. For this purpose, non-premixed combustion furnace of the Lisbon University has been investigated using the open source OpenFoam software as well as chemical calculations with the help of counter-flow diffusion flame solver. In numerical study, standard k-ε turbulence model, modified EDC combustion model, and discrete phase radiation model with the calculation of absorption and emission coefficients at six different wavelengths have been used. The results of simulations and kinetic calculations show that the change in oxidant composition and wall thermal conditions leads to changes in reaction pathways. Replacement of CO2 with N2 in the oxidant and presence of heat losses lead to fundamental changes in flame structure. The presence of wall heat loss, especially in conventional and flameless combustion regimes, leads to fundamental changes in the reaction pathways and alters flame structure, while the main contribution to the changes of flame structure is different physical and chemical properties of CO2 in comparison with N2 at conventional and flameless regimes, respectively. In the high temperature combustion regime, the contributions of physical and chemical effects are almost equal.
 
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