Effects of inner cone length on continuous rotating detonation in a variable cross-section combustor

Abstract

A variable cross-section combustion chamber with different inner cone length L is designed, composing of an annular part with divergent width and a cylinder part without inner cone. Ethylene-air and hydrogen-air continuous rotating detonation (CRD) experimental tests are conducted. The results show that the ethylene-air CRD wave can be achieved in the variable cross-section combustor with the short inner cone. The propagation velocity of ethylene-air CRD wave can be 1661.37 m/s with the equivalence ratio of 0.91 and L of 10 mm. With L increasing from 0 mm to 30 mm, the combustion mode varies in the single wave mode, the sawtooth wave mode, and the hybrid mode. The combustor width is not the main factor leading to the failure of detonation in this study. The acceleration of propellent mixture caused by the expansion of the annulus channel, and the downstream movement and reduction of recirculation zone around the inner cone both increase the difficulty in CRD realization. While the hydrogen-air CRD can self-sustain with the intensive reaction zone in the annular part in the critical configuration of ethylene-air CRD. This study will contribute to the understandings of self-sustaining mechanism of CRD in the divergent combustor and the combustor design of the hollow chamber.