A comparative study of obstacle-induced detonation initiation and flame jet detonation initiation in chambers at the same scale

A series of experiments were carried out to investigate the characteristics of detonation initiation with pre-detonators and obstacles. Chambers with a 20mm×70mm rectangular cross-section and smooth tubes with 6 mm inner diameters were used as main detonation chambers and pre-detonators, respectively. The gas mixture used in the study is oxygen/ethylene/nitrogen mixture and the nitrogen diluted ratio β is set as a variable. Flame acceleration process was captured by a high-speed camera. Three initiation modes were observed in the flame jet detonation, and only one form of detonation initiation was found in detonations triggered by obstacles. The DDT distance and flame velocity all indicate that when β ≤ 0.7, hot jet can initiate detonation in a short time, while obstacles perform better when β ≥ 1.