Experimental investigation of detonation decay in rough narrow channels

Abstract

The conditions for detonation propagation in narrow channels are of great interest for ensuring explosion safety in industrial facilities using hydrogen. The roughness of the channel walls can lead to either flame acceleration or to the detonation decay. In this work the propagation of detonation of hydrogen–air mixtures in smooth and rough narrow channels was experimentally studied. The experimental setup consisted of a 3000 mm long driver section and a 1200 mm long diagnostic section with a 7×7mm cross-section. One or two walls of the diagnostic channel were covered with sandpaper which had a grain size of 500–600μm and 80–100μm. Lean, stoichiometric and rich mixtures were used for hydrogen with air. Based on the flame velocity graphs and shock wave pressure in the diagnostic section, several flame propagation regimes were recorded, depending on the fuel concentration and channel roughness. Non-linear effect of the roughness on the detonation propagation was observed. When two pieces of sandpaper were placed on the opposite sides of the narrow channel, a drop in flame velocity to the sound speed of the combustion products was registered for hydrogen mixtures with air. However, covering one wall with small grain sandpaper could lead to expanding of the detonation limits compared to the smooth channel.