Effects of the jet obstacle on flame acceleration and deflagration-to-detonation transition: A numerical perspective

As a new type of the detonation-promoting technology, the jet obstacle has attracted wide attention of researchers, but there are still many deficiencies in the current studies. Based on means of numerical analysis, the effects of jet velocity and the non-uniformity of the velocity distribution on flame acceleration and DDT (deflagration-to-detonation transition) processes are investigated in detail using the unsteady Reynolds average simulation method. The findings indicate that, with regard to flame acceleration, an increase in jet velocity will initially impede the acceleration of the flame to a certain extent. Nevertheless, the interaction between the flame and the jet gives rise to a complex multiple acceleration mechanism (such as the intensification of flow field perturbations within the channel, an augmented accumulation of premixed gases, an amplified virtual blocking effect, and an enlarged recirculation zone). This increased jet velocity serves to accelerate both the propagation of the flame and the detonation initiation process. The jet non-uniformity of the velocity distribution is also a vital factor to improve the DDT process. With the increase in the trend of non-uniformity changes in the jet velocity distribution (the continuous enhanced jets are used in this paper), the time and distance required for the detonation initiation of premixed gases are shortened. Furthermore, depending on the state of the shock wave, the detonation initiation processes in this paper all belong to the shock to detonation transition, which can be further classified into two categories: (I) detonation that induced by shock reflection; and (II) detonation that induced by shock focusing.