Analysis of flow-field characteristics and pressure gain in air-breathing rotating detonation combustor

Three-dimensional numerical simulations are performed on air-breathing rotating detonation combustors with detailed H-2/air chemistry. Detonation-related flow structures and pressure gain performance have been investigated. Emphasis is placed on the effects of the upstream oblique shock wave that is attached with detonation. This unsteady oblique shock wave is found to rotate along the chamber in the pre-detonation region. The angle of the upstream oblique shock wave shows a negative correlation with chamber pressure. Moreover, particle trajectory analysis shows that particles cross the unsteady upstream oblique shock wave twice or three times before being consumed by detonation, with obvious deflections in the radial direction due to the curvature effect, while particles collide with the downstream oblique shock wave in the post-detonation region once. At the exit, more than 96% of kinetic energy is still concentrated in the axial direction. Furthermore, the pressure gain performance is investigated by the integral of total pressure over the averaged area in the axial direction and individual particles. The results show that detonation-related flow structures in the current chamber configuration fail to achieve positive pressure gain. -17.2%, -16.4%, and -17.8% of total pressure gain are obtained in three numerical simulations. Further analysis shows that though the total pressure of particles increases instantly when encountering the upstream oblique shock wave, 25% of total pressure is lost before detonation combustion due to the large angle of the upstream oblique shock wave and the geometry. The cumulative effect of the pre-detonation region on the total pressure is equivalent to flows with Mach 1.94 crossing a normal shock wave.