In porous burners, premixed combustion of gaseous fuels inside the cavities of an open-pore ceramic matrix heats the solid material to temperatures of 1400 °C, which leads to the emission of electromagnetic radiation with its intensity maximum at infrared light. The net thermal radiation emission can be used for efficient, fast and uniform heat transfer in various technical applications. Improving radiation efficiency correlates to increasing thermal radiation flux at constant thermal power, implicating a potential for reduction of fuel consumption and associated emissions for a given application. Additive manufacturing techniques offer new opportunities in the design of ceramic structures. However, the design of an optimized structure requires detailed knowledge of processes and conditions inside the porous matrix during operation, the experimental determination of which is complex and challenging. Inside the porous burner, chemical combustion reactions coincide with complex interaction between thermo-physical transport processes that occur within solid and gaseous phase, and across phase boundary. Flow, heat release and resulting heat flows influence each other. ... mehrThe numerical model used in this work considers gaseous and solid phases, includes flow, enthalpy transport, conjugate heat transfer, radiative heat transfer between solid surfaces as well as combustion kinetics according to a skeletal chemical reaction mechanism. These phenomena are resolved on the pore scale in three-dimensional space (Direct Pore Level Simulation, DPLS). The calculations are performed based on the finite volume method using standard applications implemented in the OpenFOAM library. The reactive flow and enthalpy field are calculated for a lateral periodical representative element of flat twolayer porous burner in full axial extension of flame trap and porous structure. The present study presents simulations of three different structures, each at four settings of specific thermal power. Results indicate that specific surface area of the porous structure is a major influencing parameter for increasing radiation efficiency, whereas no correlation of the orientation of an anisotropic structure on radiation efficiency was observed.