Evaluation of Optimized 3-step Global Reaction Mechanism for CFD Simulations on Sandia Flame D

The aim of this paper is to evaluate a new optimized 3-step global reaction mechanism (opt) [1] for a methane-air mixture for industry purpose. The global reaction mechanism consists of three reactions corresponding to the fuel oxidation into CO and H2O, and the CO - CO2 equilibrium reaction. Correction functions that are dependent on the local equivalence ratio are introduced into the global mechanism. The optimized 3-step global reaction scheme is adapted into the Computational Fluid Dynamics (CFD) analysis of a partially-premixed piloted methane jet flame. The burner consists of a central nozzle (for premixed fuel/air), surrounded by a premixed pilot flame, and an annular co-flow stream. Both steady-state RANS (Reynolds Averaged Navier Stokes) and time-averaged hybrid URANS/LES (Unsteady RANS/Large Eddy Simulation) results have been computed and compared with experimental results obtained from the Sydney burner at Sandia National Laboratories, Sandia Flame D [2]. The CFD results with the optimized 3-step global reaction mechanism show reasonable agreement with the experimental data based on emission, velocity and temperature profiles, while the 2-step Westbrook Dryer (WD2) [3] global reaction mechanism shows poor agreement with the emission profiles.