Premixed Flame Dynamics in Confined Channels: Toward Efficient Heat Generation

This study investigates the propagation of premixed flames in narrow channels under the combined influence of differential diffusion, thermal expansion, and imposed Poiseuille flow. The analysis is carried out within a variable-density framework using numerical simulations to determine both steady and time-dependent regimes.In the absence of flow, we observe multiple steady solutions, describing flames with symmetric or asymmetric shapes. A symmetry-breaking bifurcation occurs as the channel width increases, with the branch of symmetric solutions losing stability and giving rise to a branch of stable asymmetric solutions. The Lewis number Le is shown to significantly influence the flame: lower values of Le enhances the multiplicity of solutions and the emergence of asymmetric flames.When an imposed Poiseuille flow is introduced, the effective propagation speed depends nonlinearly on the flow amplitude. Time-dependent simulations reveal transitions from unstable to stable flame solutions, depending on the flow strength and the confinement. The study reveals an interesting original result: For small values of Le, a stable symmetric solution coexists with two asymmetric solutions—one stable and the other unstable.