Combustion characteristics of continuous rotating detonation in the hollow combustor through synchronous chemiluminescence imaging

This study investigates the combustion characteristics of continuous rotating detonation (CRD) in a hollow combustor using synchronous chemiluminescence imaging. Ambient-temperature ethylene and air are employed as propellants, with the air mass flow rate being 350±[jls-end-space/]10 g/s. The results show that the high-luminance zone induced by the CRD wave is attached to the outer wall while the low-luminance deflagration combustion occurs in the central region of the hollow combustor. As the nozzle contraction ratio (CR) increases from 1 to 4, the area of the deflagration reaction zone at the center of the combustor gradually expands. However, the chemiluminescence intensity of the detonation reaction zone near the outer wall of the combustor first increases and then decreases as CR increases. Moreover, the axial length and chemiluminescence intensity of the reaction zone of CRD first increase and then decrease as the CR rises. Correspondingly, the axial reaction zone of CRD wave exhibits segmented curved, continuous linear, and loose cluster structures as the CR increases from 1 to 4. An appropriate increase in the nozzle CR enhances the pre-heating effect of the central high-temperature recirculation zone on the fresh combustible mixture, thereby enhancing the CRD intensity. In contrast, excessive parasitic deflagration combustion with a large CR leads to destruction of the combustible mixture layer and further attenuates the CRD intensity. These findings provide comprehensive understanding of the CRD flowfield within a hollow combustor, facilitating an in-depth comprehension of the self-sustaining mechanism of CRD waves.