Correlation of wall heat loss with quenching distance for premixed H2/Air flames during unsteady Flame-Wall interaction

Abstract

Flame-wall interaction (FWI) of a laminar, premixed hydrogen/air flame perturbed by a pulsating inflow with excitation frequency (f) is investigated using fully resolved simulations employing finite-rate chemistry and detailed molecular diffusion. The setup is a two-dimensional (2D) V-shaped flame interacting with an isothermal wall on one side and a freely propagating flame on the other side, exhibiting a side-wall quenching and a freely-propagating mode. The impact of unsteady flame stretch on flame dynamics is characterized by the Damköhler number (Da), which is defined by the ratio of the turnover time of the oscillating inflow to the flame transit time. Da is found to directly describe the degree of flame deformation during flame propagation. During FWI, flame pocket formation is suppressed at conditions with Da close to unity. The correlation between wall heat flux (WHF) and quenching Peclet number (Peq) shows a time delay that depends on Da. A negative linear correlation can be recovered between time-averaged wall heat flux (WHF¯) with the quenching Peclet number (Peq¯), and its slope depends on the fuel equivalence ratio. For the lean hydrogen flame, the flame stretch near the quenching point leads to a decrease in flame intensity during FWI and therefore different slope of the correlation of WHF vs. Peq.