This Note is concerned with the speed of propagation of a chemical reaction in a fast, steady and non uniform flow, which may apply to flame propagation in some instances. The structure of the flow is 1) a parallel shear flow with velocity perpendicular to the average front, where the flame speed is close to the maximum flow speed toward the fresh gases 2) a periodic cellular structure where th...

We have studied flame propagation in a strained mixing layer formed between a fuel stream and an oxidizer stream, which can have different initial temperatures. Allowing the Lewis numbers to deviate from unity, the problem is first formulated within the framework of a thermo-diffusive model and a single irreversible reaction. A compact formulation is then derived in the limit of large activatio...

Porous media are often used in flame arresters because of the high surface area to volume ratio that is required for flame quenching. However, if the flame is not quenched, the flow obstruction within the porous media can promote explosion escalation, which is a well-known phenomenon in obstacle-laden channels. There are many parallels between explosion propagation through porous media and obst...

Various flame tracking techniques are often used in hydrodynamic simulations. Their use is indispensable when resolving actual scale of the flame is impossible. We show that parameters defining “artificial flame” propagation found from model systems may yield flame velocities several times distinct from the required ones, due to matter expansion being ignored in the models. Integral effect of m...

We study a thermo-diffusive combustion model for premixed flames propagating in reactive gaseous mixtures which contain inert dust. As observed by Joulin, radiative transfer of heat may significantly enhance the flame temperature and its propagation speed. The Joulin effect is at its most pronounced in the parameter regime where the medium is very transparent while radiative flux dominates conv...

Dynamics of outwardly-propagating reaction fronts inspires both fundamental and practical interests. While for the former we can mention in pass supernovae explosions and measurements of laminar flame speeds of reactive mixtures, the latter is relevant to the operation of engines and prevention of spark-initiated hazards such as accidental or intentional explosions. While a pointy-ignited, expa...

Since most of the practical combustion devices operate in turbulent environments, study of turbulent combustion is fundamentally appealing and practically important. Turbulence enhances the flame propagation by wrinkling an otherwise laminar smooth flame, leading to an increase in the flame surface area and hence the total burning rate. There have been number of studies performed to achieve a s...

Combustion kinetics ...................................................................................................................................... 1 Physical mixing and its effects on ignition, propagation and extinction ...................................................... 2 Mixing ...........................................................................................................

A methodology for solving unsteady premixed turbulent flame propagation problems in high Reynolds number (Re), high Damkohler number (Da) spatially evolving flows is developed. The method is based on Large-Eddy Simulation (LES) with a subgrid combustion model based on the Linear-Eddy Model (Kerstein, 1991). An inter-LES cell burning mechanism has been added to the present formulation to account...

We study the effect of homogenization on flame propagation in periodic excitable media, when the width of the flame is much smaller than the characteristic size of the heterogeneities.