Publication: Effect of discreteness on heterogeneous flames: Propagation limits in regular and random particle arrays
All || By Area || By Year| Title | Effect of discreteness on heterogeneous flames: Propagation limits in regular and random particle arrays | Authors/Editors* | Tang, F. D., A.J. Higgins, S. Gorosin |
|---|---|
| Where published* | Combustion Theory and Modelling |
| How published* | Journal |
| Year* | 2009 |
| Volume | 13 |
| Number | 2 |
| Pages | 319-341 |
| Publisher | Taylor and Francis |
| Keywords | |
| Link | heterogeneous combustion |
| Abstract |
In a system with discrete heat sources distributed in an inert, heat conducting medium, there exists two asymptotic regimes of flame propagation. When the flame thickness is much greater than the inter-particle spacing, the system approximates a homogeneous medium and the flame can be modeled as a continuum. In the other extreme, when the flame is very thin due to rapid reaction of particles, the heterogeneous flame can no longer be treated as a continuum since discrete effects become dominant. The effects of discreteness are characterized by a strong dependence on the spatial distribution of the sources. The present work investigates the effects of discreteness on flame propagation and demonstrates that these effects result in a propagation limit in the absence of losses. For a system of regularly spaced particles, this limit can be found analytically for one-, two-, and three-dimensional systems, although the flame exhibits a complex dynamic of bifurcations as it approaches this limit. Propagation of a flame beyond this limit is only possible through concentration fluctuations in a system with randomly distributed particles. Two-dimensional numerical simulations with randomly distributed particles show a strong dependence of the propagation limit on the size of the computational domain. A consequence of the random particle distribution is that the flammability limit can only be defined as a probabilistic outcome of the flame propagation simulations. |
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