Experimental investigation on the performance of the variable cross section rotating detonation engine

Optimizing the structure of the rotating detonation engine (RDE) is an effective way of improving its performance. In this paper, a variable cross section RDE with convergent-channel combustor (CC-RDE) is designed and compared with annular-channel combustor (AC-RDE). The operation range, propagation characteristics of rotating detonation waves (RDWs), and working performance were analyzed. In this study, the combustor outlet blockage ratios of both RDEs were equal, both being 0.35. The results show that the CC-RDE increased the propellant flow velocity, thus increasing the chemical reaction rate, and led to a comparative increase in RDW intensity of up to 185.4%. However, the higher the RDW intensity, the more likely the air plenum and the combustor were to be coupled, which shortened the range of stable operation. The RDW position under two RDEs were approximately 100 mm away from the combustor inlet. The percentages of pressure feedback and pressure pulsation in the air plenum were defined to evaluate the extent of pressure feedback. The results show that a higher RDW intensity in the CC-RDE led to a greater pressure pulsation in the air plenum. When the unstable mode appeared, the pressure feedback further increased. The heat flux of the combustor was also measured to assess the thermal environment of the RDE. The rates of chemical reaction and energy release were higher when the CC-RDE was used, and the average heat flux increased by 40.2% compared with that of the AC-RDE. Moreover, the specific thrust of the CC-RDE was increased by 40.3%.