Dynamics of centrally ignited outgrowing flames within closed vessels

The dynamics of outwardly expanding premixed cylindrical flames within closed cylindrical vessels is numerically investigated using a new confined-hydrodynamic theory. In this asymptotic model, the flame is reduced to a surface propagating at a speed derived by considering the chemical reactions and diffusive processes occurring within the thin flame zone, of thickness much smaller than the hydrodynamic length scale. Inside closed vessels, flame propagation is impacted by gas compression and the resulting increase in pressure and temperature, with the flame speed also influenced by flame stretch and the progressive reduction in flame thickness. To capture the corrugated structures resulting from the onset and evolution of the intrinsic Darrieus–Landau instability ubiquitous to premixed combustion, a hybrid Navier–Stokes/embedded-manifold numerical methodology has been developed. This approach is employed in the current study to identify the marginal stability boundary, initial flame development and nonlinear evolution while quantifying the effects of heat release, Markstein number—a lumped physico-chemical parameter characterizing flame sensitivity to stretch—and vessel size. The results provide insights into how confinement and pressure rise affect flame morphology and propagation speed in cylindrical vessels with implications for understanding spherical flames in closed-bomb experimental devices commonly used to measure flame speed under laminar and turbulent conditions.