Detonation transmission and transition in channels of different sizes

Numerical simulations were conducted to investigate two types of detonation diffraction phenomena: (1) detonation transmission From a small two-dimensional channel to a large one, both filled with the same ethylene-based mixture; and (2) detonation transition from a small channel filled with a stoichiometric ethylene-oxygen mixture into a large channel filled with a stoichiometic ethylene-air mixture. The transmission cases show that in the stoichiometic ethylene-oxygen mixture, the detonation originally generated in the small channel, containing eight pairs of triple points (8 Lambda), successfully transmits into the large channel, and in the stoichiometic ethylene-air mixture, the detonation from the small channel, containing only four pairs of triple points (4 Lambda). fails after its transmission into the large channel. In the transition case, the detonation front from the small channel also containing eight pairs of triple points (8 Lambda), survives its transition into the stoichiometic ethylene-air mixture in the large channel. It is interesting to note that die mixture in the large channel is the same as the mixture used in the transmission case where the detonation fails to transmit into the large channel. After the transition, the triple-point spacing increases from that observed when the detonation was still in the small channel. In all cases, the expansion waves generated at the exit of thr small channel weaken the detonation front From its edges. However. the expansion wave is only able to quench the detonation in the ethylene-air to ethylene-air case. Also, the reflected shocks From the channel walls can create local regions of high pressure and temperature and. therefore, re-ignite the mixture near the walls. However, the overall effect of the reflected shocks is quite limited in the cases studied here. The significance of these results to research on the pulse detonation engine is also discussed.