Burners that channel a gaseous methane-air mixture through a porous sintered matrix are widely used to produce flat flames with controlled inlet and boundary conditions. Such environments are essential for studying combustion phenomena and validating physical and chemical models. However, this study shows that even nominally identical McKenna burners with a \(25 \, \textrm{mm}\) stainless steel sintered matrix exhibit significant deviations from ideal uniformity. Detailed measurements of the spatial and temporal temperature fields within the matrix, as well as surface flow velocities, reveal substantial non-uniformities: velocity deviations of up to \( \pm 50 \%\) across the burner surface and temperature differences exceeding \(70 \, \mathrm {^\circ C}\) between center and edge of the matrix. Furthermore, the burner housing temperature increases steadily during operation, reaching over \(70 \, \mathrm {^\circ C}\) after 60 minutes, indicating limited heat removal and pronounced cooling defects. These findings demonstrate that even under nominally steady operating conditions, uniform inflow and boundary conditions cannot be assumed, which is highly relevant for many experimental combustion researchers relying on consistent burner behavior. The results highlight the necessity of accounting for such gradients when using flat flame burners to investigate sensitive combustion phenomena, such as thermo-diffusive instabilities and flame pulsation onset. To facilitate this, the 2D temperature and velocity profiles presented herein can be directly utilized by the community as realistic boundary conditions for future computational fluid dynamics (CFD) simulations of burner-stabilized flames on sintered burners.
