Propagation of a hemispherical flame over a heat-absorbing surface

Abstract

This paper presents an experimental study of hydrogen–air flame front dynamics and propagation over a heat-absorbing surface. Experimental data on the hemispherical flame propagation in hydrogen–air mixture with hydrogen content of 15% in 4.5 m3 cylindrical volume were obtained at the ignition at the centre of the bottom with energy of 5 J. The flame propagates at atmospheric pressure over a solid aluminium wall or a layer of steel wool. The flame acceleration dynamics were compared at hemispherical and finger flame stages. It was found that in a mixture with a hydrogen content of 15% the flame over the layer of steel wool propagates 2.5 times more slowly than that over the surface of an aluminium wall. Calculation of heat absorption in the steel wool layer shows that the heat losses due to the absorption are the main phenomenon causing the suppression of Darrieus–Landau instability and flame front speed reduction, which was observed in the experiments. Experimental results are compared with analytical model of finger flame propagation from literature.