Detonation transition process in a channel equipped with the repeated obstacles (Effect of obstacle height and spacing on the DDT process)

Abstract

Experiments were performed to investigate the deflagration-to-detonation transition (DDT) process in the channel equipped with repeated obstacles. A premixed gas of hydrogen-oxygen was ignited and the DDT process was visualized by using a high-speed video camera with an aid of schlieren optical method. A configuration of the repeated obstacle such as a spacing, d and a height, h were varied to investigate effects of these parameters on the detonation induction distance (DID) as well as DDT process. Furthermore, the flow-field was visualized by changing the directions of obstacle installation, such as vertical installation and transverse one. The DDT process could be clarified in detail, because the transverse installation of obstacle could acquire the flow-field in depth direction of the obstacle. As a result, it was clarified that the DDT was occurred by highly accelerated flame caused by the interaction between deflagration wave and the vortex-ring behind obstacle. Thus, the vortex-ring generated by the diffraction of compression waves was interacted with the deflagration wave, and this behavior produced a high-velocity deflagration wave through the unburned gas pocket behind obstacle. This high-velocity deflagration wave propagated in the depth direction could be a trigger of DDT onset via local-explosion. The detonation induction distance was also determined by observing a fish-scale pattern on the soot which was typical of the detonation propagation, and the relationship between DID and the configurations of repeated obstacle was also obtained.

Keywords

• detonation wave
• deflagration wave
• local explosion
• ddt
• obstacle
• visualization