Characterizations of open-cell foams for porous media combustion.
Emeric Boigné, Stanford University, Stanford, USAPriyanka Muhunthan, Stanford University, Stanford, USASadaf Sobhani, Stanford University, Stanford, USADanyal Mohaddes, Stanford University, Stanford, USAMatthias Ihme, Stanford University, Stanford, USA
Porous Media Combustion (PMC) has been the subject of constant research efforts over the past decades because of its promising combustion properties, which include extended power modulation and reduced CO and NOx emissions. Porous media burners consist of a porous ceramic foam facilitating internal heat-recirculation from the hot combustion products to the unburned reactant stream. However, the strong interaction between the porous ceramic matrix and hot combustion environment introduces significant challenges to the material properties of the porous foam. This presentation provides a detailed analysis of the competing requirements in terms of pressure drop considerations, catalytic effects, thermal transport and structural durability. To this end, commonly used ceramic materials, including alumina, silicon carbide or yttria-stabilized zirconia were considered experimentally. Open-cell foams were operated in burners over extended periods of time, and compared with respect to manufacturing techniques, burner performances, and material properties. Differences in the foam geometries were analyzed using X-ray microtomography. The topologies of the different ceramics were extracted and used to evaluate several geometric properties. Porosity, pore and cell diameters were characterized and used as input to 1D volume-averaged simulations. The pore-geometries obtained from 3D tomographic reconstructions were simulated to computationally evaluate effective conductive properties. On-going work focusing on using scanning electron microscope to further investigate catalytic effects and thermal durability are presented and further challenges encountered in one- and multi-dimensional simulations are discussed.