Performance Comparison of Variable Center Body Configurations for a 25 mm Rotating Detonation Rocket Engine

Abstract

Rotating detonation rocket engines (RDREs) are propulsion devices that harness circumferentially traveling detonation waves that consume propellants through self-regulating axial injection into the combustion chamber. This process provides theoretical benefits of combustion pressure gain and thermodynamic efficiency compared to classical, deflagration-based combustors. Because of the additional mass and the complexity of mechanical integration and thermal management for the addition of a center body in typical annular (Center Body, CB) RDREs, there is interest in exploring a cylindrical (Center Bodiless, CBL) chamber geometry. To understand the trade-offs between these two geometric configurations, particularly for small-scale devices, the performance and operational characteristics for a 25 mm with a removable 15 mm center body are compared between CB and CBL configurations using gaseous propellants including methane/oxygen and hydrogen/oxygen, and operating at varying equivalence ratios and at a total mass flow rate of 0.075 kg/s. Overall, the range of equivalence ratios for operability is smaller for the CBL geometry than the CB geometry for methane/oxygen operation, likely due to timescale considerations among the characteristic residence, detonation, and acoustic times. Additionally, the thrust and specific impulse are generally found to be 15–40% lower and the injector-face chamber pressure 20–50% lower for the CBL geometry compared to the CB geometry across both propellant mixtures. Periphery detonation wave speeds for the CBL configuration are additionally found to be 17–46% and 61–127% greater than the CB periphery detonation wave speeds for methane and hydrogen, respectively. An acoustic analysis of both chamber geometries is also shown to highlight the differences in chamber acoustic modes between these engine configurations.

Topics & Concepts