Propagation and flow field analysis of wall-detached continuous rotating detonation wave in a hollow combustor

Wall-detached continuous rotating detonation (CRD) was experimentally and numerically achieved in the designed hollow chamber. For this novel CRD wave, the pressure signals measured at the chamber wall showed lower peak pressure but much higher frequency when compared with typical wall-attached CRD. Meanwhile, the high-speed photographs showed that the luminous area (i.e. coupled reaction zone) of this CRD wave always varied within a “wall-detached” cylindrical zone. Experimental results with different ribs further proved that the CRD wave propagated within a cylinder whose diameter was about 44 mm, and the corresponding propagation velocity was very close to that of C-J detonation. A model was proposed to illustrate the flow field structure of this special CRD. According to the annular injection position of propellants, the hollow chamber was divided into two parts, namely, central CRD zone and outer shock wave zone. The detonation wave propagated within the former zone and the induced oblique shock waves stretched in both of the two zones. These two waves rotated synchronously to form the basic flow field structure of this wall-detached CRD. This model was further verified by a premixed numerical simulation case. The wall-detached propellants injection was believed to contribute to the formation and self-sustaining of the detonation wave in the center, and the oblique shock waves were induced on both sides due to the lateral expansion effect. This study shows that the detonation wave could rotate spontaneously and continuously without the support of chamber wall. The analyses on the propagation characteristics as well as the flow field structure of wall-detached CRD contribute to the understanding of self-sustaining mechanism of CRD wave in the hollow chamber.