Attenuation and recovery of detonation wave after passing through acoustically absorbing section in hydrogen-air mixture at atmospheric pressure

Abstract

The deceleration and attenuation of a detonation wave in a hydrogen-air mixture were experimentally studied in a cylindrical channel. The inner walls of an extended section of the channel were covered with an acoustically absorbing layer. Experiments were carried out in an undiluted by inert gases mixture at atmospheric pressure and 295 K temperature. Ignition of the hydrogen-air mixture was carried out by a spark gap at a closed end of the detonation tube, and the second end of the tube was opened. A strong detonation wave was formed before entering the section with the acoustically absorbing layer on the walls. The dependence of velocity and pressure at the front of the detonation/shock wave on the thickness of the acoustically absorbing material and mixture composition (equivalence ratio) was presented. The results demonstrate that increasing the thickness of the porous material on the walls lead to further attenuation of the detonation wave to the point where it is not re-initiated at the distance of 15 calibers from the porous section. It was found that the recovery of the detonation wave after the passage of the acoustically absorbing section can happen if the shock wave velocity does not drop below Chapman-Jouguet acoustic velocity.