Numerical Simulations of Confined, Turbulent, Lean, Premixed Flames Using a Detailed Chemistry Combustion Model

In this paper numerical simulations of a confined, high strained jet flame employing a detailed chemistry combustion model are presented. Unlike other configurations available in literature, the geometry under investigation presents the jet axis shifted one side of the confining chamber in order to get non-symmetric recirculation zones and a flame stabilization mechanism based on the recirculation of a high percentage of hot combustion products. Fully three-dimensional unsteady simulations are carried out with finite-rate chemistry effects included by means of a detailed reaction scheme. Turbulence-chemistry interaction is taken into account by employing a presumed PDF approach, which is able to close species source terms by solving two additional transport equations. The use of the hybrid RANS/LES SST-SAS turbulence model is able to include large unsteady turbulent structures according to the local grid size and flow conditions. The approach presented here allows an in-depth investigation of flame stabilization mechanisms, ignition phenomena and influence of recirculation regions on flame stability. Additional simulations adopting simpler combustion models (i.e. Eddy-dissipation Concept) are also presented in order to assess the prediction capabilities of methods widely used in design environments. The paper also includes experimental data while comparison in terms of radial profiles at different heights above the burner are provided.