Effect of orifice plates on detonation propagation in stoichiometric hydrogen-oxygen mixture

In this study, experiments were carried out in a circular tube (5300 mm long, 48 mm inner-diameter) filled with orifice plates to investigate the detonation behaviors of stoichiometric hydrogen-oxygen mixture. Two kinds of orifice plates, i.e., round orifice plates and square orifice plates were used to generate obstacle configurations with various spacings. The blockage ratios of these orifice plates are 0.56. Evenly spaced photodiodes were mounted on the tube wall to record the detonation velocity. Long soot foils were adopted to study the evolution of the cellular structure. The detonation propagation limits (also the quasi-detonation limits) were found to be in agreement with deff/λ > 1, where deff and λ are the effective diameter of the orifice and the detonation cell size. The measured velocity as well as the propagation limits are independent of the opening geometry as long as the effective diameters are identical. Soot foils obtained with various sensitivity (or initial pressure) exhibit that the re-initiation of detonation occurs via a variety of modes. Well within the limits, the detonation could recover via the generation of hot spots. In some cases, a detonation can propagate without the formation of hot spots. Near the limits, only a few transverse wave traces or streaks can be observed, indicating that the propagation mechanisms are changed.