Re-initiation of detonation across an inert region

Abstract

Re-initiation of gaseous C-J detonation waves across a region of air has been studied experimentally. The experimental apparatus consisted of a 9 meter long square tube with internal dimensions of 125 mm. The Random Choice Method (RCM) was used to predict the nonisentropic expansion behind a detonation wave and the shock transmission tnto an inert gas. Good agreement between numerical and experimental results was obtained. With an inert air gap of 0.1-0.2 m, detonation re-initiation occured in acetylene-air. However, under similar conditions detonation failed to re-initiate in ethylen-air. The re-initiation process did not occur instantaneously, but was characterized by a delay. The governing parameters for re-initiation were the C-J properties in the donor section, width of the inert region and the reactivity of the gas mixture in the acceptor section The re-initiation process was also influenced by the sharpness of the inert region boundary, heat transfer and friction to the tube wall and by some other wall efect, likely due to soot on the tube wall.