Experimental study on the detonation initiation using pipe bundle geometries in CH4–2H2–3O2 mixture

Abstract Effects of the pipe bundles number and position on the deflagration to detonation transition (DDT) are investigated systematically for the first time in CH4–2H2–3O2 mixture. Four pressure transducers (PCB102B06) are used to obtain the average velocity by recording the time-of-arrival of the combustion wave. Meanwhile, the soot foil is employed to register the detonation cellular patterns. The results indicate that the critical pressure for DDT is reduced significantly after the pipe bundles are introduced into the tube. The optimum position for DDT occurs at position-II. At position-I, the flame acceleration is more significant for n = 4 case, no difference can be observed among n = 3, 4 and 5 cases at position-II, and the critical pressure is lower with the increases of pipe bundle number at position-III. The process of DDT closely depends on the flame jets. Finally the parameter of DH/λ is introduced to quantify the critical condition of DDT. The critical value of DH/λ nearly fluctuates around 1 at positions-I and II, and it is far greater than 1 at position-III. This indicates that in addition to the wave propagation mechanisms, the DDT regime is also closely related to the initiation process.