Dynamics of planar flames within closed channels

The dynamics of premixed planar flames propagating within closed rectangular channels is numerically studied within the context of a hydrodynamic theory. The flame is asymptotically modelled as a surface propagating at a speed derived by considering the transport and chemical processes occurring within the thin flame zone. Unlike freely propagating flames that evolve in near-isobaric conditions, flame dynamics in closed vessels is influenced by gas compression resulting in a notable rise in pressure and temperature. In addition to the flame stretch, flame speed depends on the pressure buildup which results in a reduction of the flame thickness. A hybrid Navier-Stokes/embedded-manifold numerical methodology has been developed and is used to simulate the evolution of planar flames. This methodology is validated against exact analytical solutions and is used to study the influence of confinement, compression and increases in burning rate on intrinsic flame instabilities such as the Darrieus–Landau instability prevalent in premixed combustion. The long-time non-linear evolution of flame surface morphology, instability growth and propagation speed have been examined, quantifying the effects of heat release, Markstein number and channel length.