Attenuation of gaseous detonations by porous media of fine microstructure

Abstract

This article reports on numerical simulations of detonation propagation in channels that contain one or more porous obstructions. The porous media considered herein have high porosity and are of fine microstructure, i.e. the diameter of the fibres of the solid matrix is smaller than the characteristic chemical length scale. Our study is based on a thermo-mechanical model for flows in superposed porous and pure-fluid regions. According to it, the solid matrix is represented as a rigid continuum and its porosity is introduced as a distribution that varies in space. With regard to chemical kinetics, two different three-step chain-branching schemes are considered; their difference being in the termination reaction. Our simulations predict that, even at high porosity, the porous obstructions act as a highly efficient momentum sink, thereby causing the detonation to attenuate significantly. In the case of a single porous section, the detonation re-initiates downstream via chain-branching explosion. However, arrays of porous zones that span the entire cross section of the domain produce a decoupling of the reaction zone from the leading shock, thereby effectively suppressing the detonation. Also, our study reveals that in domains with arrays of porous blocks that only partially cover the cross section of the channel, the detonations do not quench. Instead, they propagate as low-velocity detonations, the properties of which are elaborated herein as well.