Impact of combined fluid-solid obstacles on flame acceleration and deflagration-to-detonation transition in a non-uniform concentration field

The paper employs the unsteady Reynolds-average Navier-Stokes method to model the flame acceleration (FA) and deflagration-to-detonation transition (DDT) processes of hydrogen/air premixed gases in the channel. By varying the distance (S1) from the first fluid obstacle to the left wall, its impact on FA and DDT processes is investigated. The results indicate that variations in the jet position significantly influence the processes of FA and DDT. Specifically, during the initial phase of FA, FA is affected by both fluid and solid obstacles, and the FA effect is better only when the value of S1 is small. Reducing S1 can effectively shorten the DDT time, but a compromise needs to be considered when attempting to reduce both the time and distance of the DDT process. Although fluid obstacles can facilitate FA, this impact gradually diminishes over time, especially when S1 exceeds 250 mm. In this paper, the optimal results for DDT time and distance are achieved when S1 is set to 100 mm. Finally, the process of detonation initiation can be categorized into three types: (I) detonation triggered by the interaction between the leading shock wave and a solid obstacle; (II) detonation resulting from the coupling of the flame surface with a high-pressure point; (III) detonation initiated through the interaction of the flame with the reflected shock wave.