Hydrogen-Air Flame Propagation in a Tube with Heat-Absorbing Lining

Abstract

The paper presents experimental investigation results concerning combustion of initially stationary hydrogen-air mixture in a tube, one of the walls of which is lined with steel wool, a fibrous absorbent material. We used a schlieren photograph series imaging the cellular flame to obtain the distance traversed by the flame front as a function of time for the case when lining is absent and for three cases of steel wool lining of varied thickness and porosity. The paper shows that flame propagation rate in the hydrogen-air mixture containing 15 vol % hydrogen in a tube featuring a circular cross-section with a diameter of 54 mm when lining is present is up to 3 times higher than the flame propagation rate in a tube without lining. We calculated the density, heat capacity and thermal conductivity for the steel wool. We also calculated heat emission rate during combustion and the rate at which the steel wool layer absorbs heat from the region occupied by combustion products. We determined the percentage of heat energy absorbed by the steel wool and analysed how this effect affects flame propagation rate. We measured cell dimensions in an unstable flame propagating in a tube with and without lining. For the case of a flame front propagating across a fibrous absorbent material layer, we found that the average cell size observed decreases twofold