Influence of modelling and scenario uncertainties on the numerical simulation of a semi-industrial flameless furnace

Flameless combustion is able to provide high combustion efficiency with low NOx and soot emissions. The present work aims at investigating the role of closure sub-models for the modelling of a flameless furnace, as well as the main NO formation paths. Among the different turbulence models that were tested, modified k–ɛ provides the best agreement with the experimental data, especially for temperature measurements. Reynolds stress model leads to smaller deviation for radial velocity predictions. Since in flameless combustion regime the turbulence–chemistry interaction as well as the kinetic mechanism play a fundamental role, the Eddy Dissipation Concept (EDC), coupled with four different kinetic schemes (JL, KEE58, GRI 2.11 and GRI 3.0) was considered. The GRI 2.11 and KEE58 mechanisms perform better, thus confirming the necessity of turbulence/chemistry interaction models accounting for finite-rate chemistry when flameless combustion is studied. As far as NO emissions are concerned, the N2O intermediate NO mechanism is found to play a major role, while thermal NO formation mechanism is not as relevant as in traditional combustion regime. essment of the uncertainty related to the choice of boundary conditions as well as to the choice of the parameters of the physical models is also performed. Finally the operation characteristics (such as the recirculation rate and the location of the reaction zone) of the furnace are evaluated.