Comparative Study of Detonation Initiation Methods via High-repetition Rate Chemiluminescence Imaging at 150 kHz

The pre-detonator and obstacle have been demonstrated as two main approaches that can initiate the fast and reliable detonation for detonation based engines. To compare the capabilities and limitations of the two approaches for detonation initiation, a series of experiments were performed under different operating conditions, and the chemiluminescence images were recorded at 150 kHz. The results demonstrate that there are four initiation modes for the pre-detonator method, and each mode corresponds to a specific initiation delay time and deflagration to detonation transition (DDT) distance. While for the obstacle method, the initiation delay time and DDT distance are mainly dependent on the reactivity of mixtures. The quantitative comparisons of flame tip velocity show that: 1) the pre-detonator method outperforms the obstacle method for the high reactive mixtures since it induces the direct detonation initiation at the entrance of the chamber; 2) for the low reactive mixture, the success rate of detonation initiation by obstacle is higher than that by pre-detonator.