Numerical investigation of operational performance in a methane-oxygen rotating detonation rocket engine
Christopher Lietz, Mathias Ross, Yogin Desai, William A. Hargus
Abstract
This work examines a rotating detonation rocket engine (RDRE) using large eddy simulations (LES) of a three-dimensional domain with discrete fuel and oxidizer injector orifices. The case follows an experimental set-up from the Air Force Research Laboratory (AFRL) with high-pressure gaseous CH4 and O2 as the reactants. Six high-fidelity computations are used to study the effects of varying equivalence ratio and mass flow rate as well as the addition of a throat at the end of the combustion chamber. The analysis first makes comparisons against available experimental results from qualitative and quantitative perspectives. In all instances, the simulations closely capture the macroscopic engine behaviors with minor deviations attributed to model choices. The focus then moves to examining the flow fields during stable operation, contrasting the simulations by means of detonation surfaces, spatially-averaged plots used for visualizing time-varying fields. From this reduced dimensionality, several trends are noted and observations can be made more readily. Increasing the mass flow rate over nominal conditions yields a scaled-up behavior containing nearly identical physical features but higher pressures, thrust, and Isp. In contrast, increasing the equivalence ratio leads to a divergence in the flow: substantially more waves are present in a dual-directional or slapping mode that dramatically alters the qualitative result, but fails to generate significant performance gain. Finally, the addition of a downstream constriction inevitably chokes the exiting mixture and adds thrust, while yielding counter-rotating waves and more parasitic deflagration.