Three-Dimensional Numerical Simulations of Turbulent, Bluff-Body Stabilized, Lean, Premixed Combustion

Abstract

Results from three-dimensional (3D) unsteady numerical simulations of turbulent, bluff-body, stabilized, lean, premixed combustion are reported. Shear stress transport (SST) k − ω model has been used for modeling turbulence, while a detailed 43-step mechanism has been used for modeling the methane, air chemistry. Turbulence chemistry interaction has been modeled using the eddy dissipation concept. Calculation has been done with buoyancy effects included to account for the effect of buoyancy on the predicted results. The three dimensionality of the flame is clearly demonstrated through velocity and temperature profiles. The intensity of turbulence is greatly enhanced by the flame, which is located at the shear layer, and thus the role of the flame as a turbulence generator is highlighted. The shear layer separates the cold reactants and the hot products, and is thus highly strained. The spectral analysis of time histories of pressure and velocity reveal that the lowest and highest dominant frequencies correspond to the vortex shedding mode and instability mode, respectively. Predicted numerical results [both mean as well as root mean square (RMS) values] are compared with the experimental data reported by Nandula et al. (S. P. Nandula, R. W. Pitz, R. S. Barlow, and G. J. Fiechtner, Rayleigh/Raman/LIF Measurements in a Turbulent Lean Premixed Combustor, AIAA-96-0937, 1996).

Keywords:

• Bluff-body stabilized
• Confined flame
• Lean mixture
• Numerical simulations
• Premixed flame
• Turbulent combustion

ACKNOWLEDGMENTS

The authors wish to thank the reviewers for their insightful comments and suggestions. The authors further wish to thank the Product Group, DELL Inc. for partially supporting this work through a hardware donation and the P. G. Senapathy Computing Center, IIT Madras for providing the required software license. Discussions with Dr. Raghavan regarding the radiative corrections and simulations of premixed flames are also acknowledged.