Effects of porous wall on deflagration to detonation transition and detonation wave propagation

To study the influence of a porous wall on the initiation and propagation of the detonation wave, experiments with ethylene and oxygen-rich air are carried out. The effects of oxygen content ( β ) on oxidant, pore density of porous media, and equivalent ratio are analyzed with technologies like chemiluminescence, schlieren, and soot foil. The results show that the detonation wave bends due to the mass divergence into the porous wall. With the increase in oxygen content in the mixture, the curvature of the wave surface decreases, and the local decoupling and re-initiation of detonation disappear. Regarding the pore density, porous walls with smaller pores (10 ppi) have the strongest flame acceleration capability. The deflagration to detonation transition distance is the shortest and the velocity deficit is the largest. As for the equivalent ratio ( ϕ ), a deflagration wave is observed in the condition β = 0.5, ϕ = 0.5. Successful detonation is observed in the range ϕ = 0.6-2.2. The detonation capability of the gas mixture is highest with ϕ = 1.4. As the equivalent ratio decreases from 1.4 to the fuel-lean conditions, the detonation wave is attenuated by the porous wall much more obviously. Detonation fails at ϕ = 0.6.