A Two-Dimensional Numerical Simulation of Combustion and Heat Transfer in Radiant Porous Burners

Abstract

Premixed combustion inside a porous medium is presently under investigation due to the characteristics of this technology, which provides controlled flames. The authors present numerical methods for the simulation of premixed methane/air flames in porous media using a 6-step reduced mechanism. The laminar 2-dimensional model is based on a macroscopic formulation of the heat and mass transport equations for laminar flow. The finite volume method is used for simulation with a boundary-fitted nonorthogonal coordinate system. The effects of the model on temperature and species are examined in 2 porous burners with different geometries and materials. The results are compared with the experiments available in the literature. In the first reactor analyzed, the CO mass fraction calculated is compared with the available experimental data. The good agreement with the experimental data suggests that the numerical model is an excellent tool to investigate pollutants formation. In the second reactor studied, the temperature field calculated is compared with experimental data. The effect of an injection plate at the entry of the burner is predicted, the 2D field of temperatures and mass fractions of species, giving an insight of the 3D profile of the flame. The strong advective effect caused by the acceleration of the flow due to the injection plate causes a conical flame shape. The numerical simulation of the conical flame predicted the temperature field and the flame position. A sensitivity study to the Rosseland mean attenuation coefficient, to the thermal conductivity of the solid and to the porosity is presented. It is shown that the properties of the preheating region do not significantly affect the CO emissions at the exit of the reactor, although the properties of the combustion region have a strong influence.

Keywords:

• Numerical simulation
• Porous media burner
• Premixed flame

ACKNOWLEDGMENTS

The authors are thankful to CNPQ, Brazil, for their financial support during the preparation of this work, and also thank Dr. Carla S. Tafuri Marques and the IEAV (Instituto de Estudos Avançados) for the license acquisition of Chemkin 4.1 and the permission to use it.