Effects of annular channel widths on wave system structures in wall-detached rotating detonation

The propagation modes and flow characteristics of wall-detached rotating detonation waves (RDWs) are numerically investigated by solving the three-dimensional Navier-Stokes equations in annular combustors with varying channel widths. This study highlights the crucial role that channel width plays in the evolution of wall-detached RDWs, and systematically investigates and elucidates the detonation wave acceleration phenomenon. The results show that RDWs can maintain self-sustained rotation without wall confinement, and two new propagation modes emerge, governed by geometric scaling parameters. In wide channels, the direct interaction between oblique shock waves and the walls leads to the formation of asymmetric multi-wave structures, which challenges the predictions of traditional single-wave propagation models. In contrast, in narrow channels, the RDW exhibits a concave wavefront structure with propagation velocities exceeding the Chapman-Jouguet (C-J) detonation speed, resulting from coupled interactions between recirculation zones and oblique shock waves. In addition, wall-detached RDWs demonstrate better thermodynamic performance compared to wall-attached RDWs, with notably lower heat flux at the combustor walls. These findings, which reveal new mechanisms of shock-wave-wall interactions and the morphological diversity of three-dimensional wave systems under geometric constraints, provide valuable theoretical insights for optimizing the design of high-frequency rotating detonation combustion chambers.