Experimental investigation of ethylene-fueled ramjet rotating detonation engine with an annular combustor

Abstract

Abstract A ramjet-mode rotating detonation engine fueled by ethylene is designed to demonstrate the feasibility of rotating detonation organization in annular combustor under high-speed incoming flow condition. The incoming flow with the design total temperature of 860 K and Mach number of 2 at the isolator inlet is provided by an air-heater, and the total mass flow is about 1.0 kg/s. The results show that the ramjet rotating detonation engine can operate in detonation mode when the equivalence ratio (ER) is no less than 0.54. By high-frequency pressure analysis and optical observation, two propagation modes of detonation wave are observed: rotating detonation in the ER range of 0.54-0.71 and longitudinally pulsating detonation in the ER range of 0.82-0.97. In rotating detonation mode, the wave velocity increases as ER increases, and the detonation velocities are about 60% of the CJ value. In longitudinally pulsating detonation mode, the propagation frequencies of the detonation wave are in the range of 1010 Hz-1017 Hz, which is much lower than that in rotating detonation mode, and the upstream propagation velocity of the detonation wave is estimated as 964 m/s. In addition, the maximum static pressure in the combustor increases with the ER from 0.54 to 0.97, and reaches 0.24 MPa when ER is 0.97. When ER is no more than 0.58, the isolator can effectively suppress the back pressure in the combustor, while ER is no less than 0.71, the back pressure in the combustor affects the flow at the isolator inlet, which implies that the isolator design needs to be optimized.