Effect of channel expansion angle near injector outlet on a rotating detonation engine performance

A rotating detonation engine (RDE) is expected to achieve a pressure gain (PG) in which the total pressure of the product at the engine exit exceeds the total pressure of the supplied oxidizer. However, many non-ideal phenomena exist in the RDE, which hinder the achievement of a PG. This study focused on the channel expansion angle near injector outlet which is considered to impact the structure of detonation wave and the PG performance. Combustion tests were conducted by varying the channel expansion angle near the axially injected oxidizer injector outlet to 90\(^{\circ }\) and 30\(^{\circ }\). As a result, the thrust was not affected by the expansion angle, but the propagation velocity of detonation wave at an expansion angle of 90\(^{\circ }\) was approximately 5% higher than that at an expansion angle of 30\(^{\circ }\). A comparison utilizing the pressure increase ratio obtained from the fluctuating pressure in the combustion chamber suggested that the Mach number of the detonation wave was higher for an expansion angle of 90\(^{\circ }\). As a result of evaluating the PG performance utilizing the equivalent available pressure obtained from thrust measurements, it was not confirmed to differ with changes in the expansion angle.