and equivalence ratio. Beyond the flame, where minimal chemical heat release occurs, heat is convectively transferred from the post combustion gases into the solid. Heat then conducts and radiates through the solid structure upstream through the flame. Within the preheating region, heat is again convectively transferred from the solid structure to the gas. The flame structure inside the porous matrix has been imaged by using X-ray absorption. To evaluate the temperature within the gas phase, the reacting mixture was diluted with Krypton: an inert gas that has a large X-ray absorption coefficient. References Combustion