Experimental study on the effects of the throat heights of the air annular slot on the rotating detonation waves

In order to investigate the effects of the throat heights of the air annular slot on the rotating detonation waves, experiments have been carried out while varying the throat height of the air annular slot (i.e., 0.5, 1.5, 2.5, and 4.0 mm), the mass flow rate of oxidizer (35-300 g/s), and the equivalence ratio (0.15-1.8). Air and ethylene have been utilized as oxidizer and fuel, respectively. The experimental results indicate that rotating detonation waves can be obtained under different inflow conditions, and two operating phenomena were observed, i.e., the detonation cases (the single-wave mode and the oscillation mode) and the deflagration cases (the deflagration mode and the chaotic mode). The effects of the throat height on the operating range of stable rotating detonations are related to the minimum mass flow rate of oxidizer. As the throat height increases, the minimum mass flow rate of oxidizer also increases. Furthermore, the relationship between the minimum Mach number to obtain rotating detonations at each throat height and the throat height has been obtained. Moreover, the effects of the eccentricity ratio of the air annular slot on the propagation modes have also been demonstrated.