Phenomenon and analysis of direct initiation of detonation using multiple turbulent flame jets

This work reports experimental investigations on the direct initiation of detonation using multiple turbulent flame jets, with a special focus on the arrangement schemes and fundamental physics in the initiation processes. Results show that the direct initiation of detonation can be achieved using turbulent jets even when the jet tube diameter is much smaller than the empirical critical tube diameter due to flame-shock-wall interactions. Conspicuous evidence has been shown that the probability of the direct initiation increases significantly near the detonatability limit using multi-jets compared to a single jet. These results are found to be closely related to several new phenomena observed when using multiple jets to initiate the detonation. They are: (1) unexpected rapid promotion of the final-stage flame acceleration in ignition tubes by multiple jets, which is attributed to the fact that the expanding precursor shock waves propagate back into the adjacent tube and interact with the flame; (2) enhancement of hot spot generation by multiple jets due to the precursor shock intersection and the formation of an induction zone; (3) obvious velocity loss of impinging jets initiation as a result of induced hot spots propagation in the burned gases.