Experimental Study of a Racetrack-Type Rotating Detonation Rocket Engine with Shear-Coaxial Injectors Run on Gaseous Methane and Oxygen

A model Rotating Detonation Engine (RDE) has been developed at The University of Alabama in Huntsville that facilitates study of cyclical detonation and injection processes within the combustor section during operation. The engine is a 4-inch “Racetrack” type combustor designed with optical access to the injection and combustion region via the use of flat windows that minimize unwanted lensing effects. The engine was tested with Gaseous Methane (CH4) and Gaseous Oxygen (GO2) across a range of operating conditions in order to validate operability and characterize performance. Propellants are injected through 50 discrete GO2-centered shear-coaxial elements, spaced evenly along the centerline of the combustor channel. The engine was tested over total propellant mass flow rates from approximately 0.10 to 0.45 lbm/sec (0.045 to 0.20 kg/sec) and equivalence ratios from 0.64 to 2.8. Detonation waves were observed in 4, 6, and 8 counterpropagating wave modes with average wave speeds ranging from 3447 to 4680 ft/sec (1051 to 1426 m/sec). The number of waves appear to be correlated to the average wave velocity, with the highest velocities observed in the 4-wave mode. Detonative operation was observed across equivalence ratios from 0.64 to 2.04, with the highest wave velocities observed at approximately 1.75.