Promotion of deflagration-to-detonation transition by repeated obstacle rods

the run-up distance to DDT, obstacles were installed in a tube or channel promote the flame acceleration in the initial phase. A spiral-coil the Shchelkin spiral or orifice plates frequently used as obstacles 1988) 2001) 2002) 2012). Furthermore, the roles of these obstacles in the two DDT phases have been clarified to some degree. When orifice plates are continuously arranged in a channel, the flow induced by the flame repeatedly experiences contraction and expansion. These periodic contractions and expansions cause flame folding, resulting in flame acceleration (Ciccarelli et al., 2005). By contrast, strong shock waves are formed by an accelerating flame, and reflected by the obstacles (Gamezo et al., 2008). Then, the reflected shock waves generate hot regions that produce detonation via the Zel’dovich gradient Abstract We experimentally investigated the promotion of deflagration-to-detonation transition (DDT) in hydrogen–air mixtures contained in a tube in which straight-shaped rods were installed as obstacles. In the experiments, the number of obstacle rods, their spacing, their blockage ratio, and the equivalence ratio of the hydrogen–air mixture were varied as the governing parameters. The obstacle rods had a spacing of 10 or 20 mm and a blockage ratio of 0.32, 0.41, or 0.51. As a result of an optimization of the obstacle-rod conditions, when fourteen rods, whose blockage ratio was 0.32, were installed in a tube with a spacing of 20 mm and with a hydrogen–air mixture with equivalence ratios from 0.8 to 1.2, the run-up distance to the DDT was shortened to approximately 20 times the tube diameter.