Flame Curvature in Heat-loss-affected Lean Hydrogen Flames: A One-dimensional Manifold Approach

Curvature effects are incorporated into a one-dimensional composition-space formulation of a non-unity Lewis number lean premixed flame with strong heat loss. The results of this new canonical problem successfully compare with direct numerical simulations (DNS) of a lean hydrogen-air flame propagating in a narrow channel with heat conduction through the confining plates. The complex dynamics of the flame front, consisting of isolated flame kernels, are analyzed through the various terms arising from the projection of the fuel and energy equations onto a moving scalar reference frame attached to the reaction zone. Novelty and significance statement A novel one-dimensional flame model incorporating curvature and differential diffusion effects is introduced to address non-unity Lewis number lean premixed flames with strong heat loss. This canonical flame model arises from the projection of temperature and fuel gradient magnitude onto composition space. The framework is employed to analyze flame front dynamics and identify the reaction zones governing flame kernel propagation and heat release. The composition-space flame structure shows strong agreement between the canonical problem and direct numerical simulations (DNS) of a lean hydrogen-air flame propagating in a narrow channel with heat conduction.