Description: Rotating Detonation Engine (RDE) design is challenging due to the lack of in-depth understanding of many key mixing and combustion processes. The RDE flow field is a nonuniform mixture of fuel and oxidizer concentrations with strong injector effects, large turbulence effects, multiple shockwaves, and shear layers. These inhomogeneities can lead to significant combustion inefficiencies which have a pronounced effect on the performance. The proposed research effort will transition state-of-the-art, time-resolved measurement techniques to RDEs to provide new information critical for evaluating the predictive capability of high-fidelity numerical models. This will include ultra-high-speed (100 kHz – 5 MHz) in-situ spatially and temporally resolved imaging of the oxidizer-fuel mixing (quantifying the mixing and local O/F ratio), back mixing of combustion products with fresh propellants, temperature, and species concentrations. This effort will leverage the recent advancements from MHz-rate pulse-burst laser technology for application in rocket RDE environments as well as RDE simulations to enable one-to-one comparison between measured and modeled quantities. The Phase 1 overall goals are twofold: (1) demonstrate a mixing measurement diagnostic in the linear RDE that achieves spatially and temporally resolved images of the fuel mixing and O/F measurements at rates of at least 100 kHz, (2) modeling of the RDE, moving towards anchoring simulations with measurement data. Simulations of an annular, optical RDE, undertaken during Phase 1, will guide the transition and development of additional measurement diagnostics on the annular RDE during Phase 2. The outcomes of the research effort will lead to the development of validated accurate computational tools that can be used for simulation of the laser-based signals, guide diagnostics development, and design RDE technologies.

Benefits: The proposed work seeks to modernize the measurement technology in RDEs for rocket applications. This includes time and space resolved measurements inside the RDE leveraging new technological developments such as the pulse burst laser. Detailed measurements of the mixing, O/F ratio, quantified deflagration versus detonation, and other key RDE phenomena will be directly compared to numerical simulations to provide boundary conditions and anchor current and future RDE modeling efforts.

Non-NASA applications of the proposed efforts include high-fidelity, spatiotemporal analysis of highly dynamic phenomena and validated modeling. Commercial applications include air-breathing propulsion, stationary power generation, and fundamental research in a wide range of aerothermal flows.