Experimental Research on Internal Flow Structure of Cylindrical Rotating Detonation Engine Using Ethanol

Abstract

Rotating detonation engine (RDE) is one of the combustors using detonation waves and is expected to simplify the system and improve thermal efficiency due to their hypersonic combustion and compression performance by shock waves. Most of these studies use gas propellants, and liquid propellants are rarely used, and it is important to evaluate the performance of RDE with liquid propellants. In this study, a cylindrical RDE, which is an RDE without inner cylinder, with a liquid ethanol and gaseous oxygen was tested when mass flow rate "m" ̇ was 16.5-62.0 g/s, equivalence ratio Φ was 0.42-1.46, and the back pressure pb was 13.0 ± 0.8 kPa. to evaluate operating characteristics, internal visualization, and thrust performance. As a result, Detonation was not observed when the equivalence ratio was greater than the stoichiometric value. Moreover, the combustor length decreased, detonation was not observed at any equivalence ratio when a total mass flux was 101±6 kg/(m2-s). Moreover, it is found that the equivalent ratio at ignition has a significant effect on successful ignition and combustion. Detonation was also observed when the total mass flux increased. These results suggest that combustor length, equivalent ratio, and total mass flux affect the propagation mode of a liquid RDE. Moreover, the propagation velocity is almost consistent with the acoustic frequency calculated by sound speed. From visualization results of different equivalence ratio, the brightness value distribution, pressure distribution, and composite image show that the main combustion area is almost the same. In thrust performance, a high specific impulse compared to the ideal specific impulse is achieved regardless of equivalence ratio and total mass flux. The thrust using control surface matched well with the experimental thrust.