Propagation Mechanism of Detonations in Rough-Walled Tube

Abstract

Detonation propagation mechanism in rough-walled tube has been examined in the present study. To generate wall roughness, spirals with rectangular cross section of various wire lengths are used. Detonation velocity is measured by photodiodes along the length of the tube as well as a high-speed camera for detonations with weak illumination. A short length of the smoked foil is inserted into the core of the tube at the end of the test section to register the cellular pattern. It is observed that in rough tubes with spirals, detonation velocity can vary continuously from close to the theoretical Chapman-Jouguet value far from the limit to about 40% V_CJ where the detonation fails. This contrasts with the detonations in smooth tubes, where the detonation velocity seldom decreases to less than 80% V_CJ at the limit. It is found that an abrupt drop in velocity exists when decreasing the initial pressure for mixtures with high argon dilution, indicating a transition from a quasi-detonation to a high-speed deflagration. Smoke-foil studies indicate a transition criterion from a quasi-detonation to a fast deflagration in a rough walled tube, is d/λ ≈ 1.