Numerical Study of the Transition from Turbulent Flame Jet to Detonation in a Tube with a Single Obstacle

In the present study, a large eddy simulation (LES) of the flame acceleration and the transition from turbulent flame jet to detonation in a tube with a single obstacle containing premixed stoichiometric hydrogen-air was conducted. The subgrid-scale combustion was represented by the artificially thickened flame (ATF) approach. For detailed modeling of chemical reactions effects on the present phenomenon, a 21-step kinetic scheme was used. In situ adaptive tabulation (ISAT) method was also exploited to reduce the computational cost of using detailed chemistry. The present results show that the proposed LES/ATF/ISAT approach well reproduces the physical phenomenon that occurs during the flame propagation and the transition from turbulent flame jet to detonation. It is observed that the flame behavior and the detonation initiation are influenced by tube walls. Indeed, detonation initiation occurs close to the wall and behind a Mach stem which is formed due to reflection of the leading shock from the wall. Morever, the detonation initiates following a series of local explosions that occurs behind the leading shock.