Influence of porous walls on flame front perturbations in hydrogen-air mixtures

The evolution of flame front perturbations during propagation in a half-open channel with a porous coating was studied. The porous coating generates disturbances in the flow and affects the magnitude of the disturbance of the flame front and its speed. Polyurethane foam with open pores was used as the porous coating. A series of experiments was carried out in a hydrogen-air mixture at atmospheric pressure. Mixture compositions and pore sizes varied. The molar excess of fuel (equivalence ratio) phi ranged from 0.3 to 1.0. Pore sizes ranged from 0.3 mm to 2.5 mm. Diagnostics were carried out using a high-speed camera and the Schlieren method was used for assessment. Based on the frame analysis, the sizes of the flame front perturbations were determined depending on the mixture composition and the pore size. The perturbation sizes are divided into two groups and the size increases as the average pore size enlarges. The parameters of the disturbances in the channel with porous coating and in a smooth channel are compared. Porous coatings have different effects on the size of the flame front disturbances and the flame velocity, depending on the average pore size for different equivalence ratios phi. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.