One- and two-headed quasi-planar hydrogen premixed flames

Lean highly-diffusive mixtures of hydrogen-air configure a reactive media that enables the potential propagation of reacting kernels in gaps exposed to fuel leakage. In this work, a study on nearly-two-dimensional reacting fronts under canonical configurations is proposed.

A flame sheet model is used to elucidate the mathematical existence of steady propagating solutions of temperature and reacting species fields related to semicircular flames. To this end, two physical mechanisms are proposed, convection and local heat losses, which enable the otherwise unattainable planar canonical solutions in a quiescent environment. Theoretical base steady flows in the flame-sheet limit enable subsequent studies on the stability and evolution of these type of structures.

Numerical validation is achieved via an in-house finite-element code for reactive flows in the low-Mach approximation. A quasi-2D description of the conservation equations with a one-step Arrhenius chemical model and off-the-plane conductive heat losses is used to simulate lean hydrogen-air premixed flames that slowly propagate against weak convective streams of reactants. In particular, two-headed and semicircular flames are recovered as heat losses are increased.