Internal Flow Structure in Rotating Detonation Engines with Non-Constant-Area Channels

A rotating detonation engine (RDE) featuring two fixed channel geometries, with angles [Formula: see text] (converging) and [Formula: see text] (diverging), was investigated experimentally. Optical observations, pressure measurements, and thrust measurements during gaseous [Formula: see text] combustion tests were conducted to investigate the effects of axial flow speed on detonation waves and the acceleration process of the internal flow. The results were compared with [Formula: see text] combustion data to assess how heating value affects the internal flow. An acrylic wall was used to capture the side view of the internal flow, and a stainless-steel wall equipped with eight or nine pressure ports in the axial direction measured pressure. Combustion tests were performed under both low-back-pressure and atmospheric conditions. Strong circumferentially propagating [Formula: see text] luminosity and a broadband chemiluminescence area were observed from the side of the RDE. A high-luminescence area propagating downstream of the main combustion region was inclined backward or forward relative to the direction of propagation, depending on the channel’s angle. The time-averaged pressure distribution suggested that the internal flow accelerated to critical speed in the middle of the engine within the diverging channel and near the exit in the converging channel, indicating distinct acceleration mechanisms depending on the channel angle.