Flame structure controlled by thermal radiation in a porous medium.

Abstract

This paper describes the structure and burning velocity of a methane-air premixed flame stabilized one-dimensionally in a spongy highly porous medium. The combustion gas enthalpy is effectively converted into thermal radiation emitted from the porous medium at the downstream side of the reaction zone. On the other hand, the thermal radiation incident from the downstream side is absorbed by the porous medium and is effectively converted into an enthalpy increase of the mixture at the upstream side. As a consequence, it is demonstrated that the burning velocity in the porous medium is increased by energy recirculation created from radiation heat transfer by as much as three times compared with that of a gas-phase flame. Further, the amount of radiation heat loss from the upstream end of the porous medium was measured accurately. his plays an important role in the characteristics of the flame holding. As a result, it is also demonstrated that a flame can be held in the porous medium over a wide range of flow velocities and equivalence ratios of the mixture.