Abstract

In this study, experiments were carried out to investigate the detonation velocity behavior near limits in rough-walled tubes. The wall roughness was introduced by using different spiral inserts in 76.2-mm-diameter, 50.8-mm-diameter, 38.1-mm-diameter, and 25.4-mm-diameter tubes. Different pre-mixed mixtures, CH4 + 2O2, C2H2 + 2.5O2, C2H2 + 2.5O2 + 70%Ar, and 2H2 + O2 were tested in the experiments. Different spiral wire diameters were used, and the pitch of each spiral was twice of the diameter to keep the same level of roughness in all experiments for each tube. Fiber optics were used to record the detonation time of arrival to deduce the velocity. The normalized velocity V/VCJ and the velocity deficit δ were computed and analyzed to describe the detonation behavior near the limit. The cellular structure near the limit was recorded by the smoked foils.