Kinetic and Transport Effects of Pressurized Methane Flames in a Boundary Layer

• We have recently modeled combustion of lean methane-air [1] mixtures in a boundary layer flow using the program CRESLAF [2, 3 and 4]. A uniform fuel-air mixture above the auto-ignition temperature was introduced at the inlet edge of the wall, which gave an arrested flame zone, propagating in the upstream direction with a local flame speed that is equal and opposite to the local flow velocity. We compared the interaction of this flame with three model wall materials representing three idealized cases from a chemical point of view, a completely inert wall, a radical recombining wall, and a wall supporting catalytic combustion. Here we report on an analogous study of a flame geometry that may be considered a combination of a one-dimensional flame propagating towards a wall and the combustion of a uniform fuel-air mixture in a boundary layer flow. In contrast to our previous work [1] where we had a uniform inlet flow composition consisting of unburnt gas, here there is only unburnt gas close to the walls while there is burnt gas in the center of the channel. The present study concerns lean pressurized methane flames propagating toward hot isothermal walls where chemistry on the wall is considered important. The main purpose is to compare the results with those obtained in Ref. [1], which enables us, for the same flow field (boundary layer flow), to compare the effect of flame geometry on the wall effects. We have found and have been able to explain theoretically that such subtle changes of the flame geometry, which would be rather difficult to study experimentally, may have surprisingly significant effects on the combustion process.

Nyckelord

SURFACE; COMBUSTION; REACTOR

NATURAL SCIENCES

NATURVETENSKAP

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)