A study of detonation re-initiation through multiple reflections in a 90-degree bifurcation channel

The aim of this study is to reveal the detailed process of detonation re-initiation through multiple reflections and to investigate the mechanisms that could contribute to the final re-initiation after several successive reflections. In order to observe the dynamic changes of the phenomenon using different complementary approaches, Schlieren photography, soot foil visualization, planar laser induced fluorescence (PLIF) and numerical simulations have been employed. According to the experimental results, it was discovered that the second last reflection is the most critical for re-initiation instead of the last reflection. This is because during the second last reflection, multiple transverse waves can be generated. They were observed to interact with one another and form the cellular-shaped structures which resemble the transverse waves in a typical detonation wave. Regarding the origin of the multiple transverse waves, they were observed to originate from a local explosion at the second last reflection. The local explosion could also convert a transverse shock into a transverse detonation, which was proven to be essential for the successful re-initiation process under the present testing conditions. Numerical simulations were implemented which can successfully re-construct the general re-initiation pattern with multiple transverse waves. It also revealed a unique transverse wave proliferation mechanism which can explain the further evolution of the transverse waves.