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Rotating detonation rocket engine analysis with high-speed optical diagnostics


This dissertation details design and experimental analysis of the rotating detonation rocket engine (RDRE) propulsion concept, which offers potential gains in specific impulse and thrust-to-weight relative to conventional deflagration-based rockets. A liquid bi-propellent RDRE test article has been designed for use with hypergolic space-storable propellants leveraging additive manufacturing to improve hydraulic performance. High-speed imaging is performed to characterize detonation formation times, measure detonation wave-speeds, and assess the detonation wave modes in the combustor during hot-fire testing. These detonation characteristics are correlated with combustor performance metrics, such as thrust and specific impulse. These data are also used to make the first estimates of the detonation cell size for these propellants, which cannot be measured using conventional techniques. Additionally, MHz optical diagnostics have been developed using laser-absorption spectroscopy (LAS) with distributed-feedback (DFB) lasers for sensing time-resolved pressure, temperature, and CO/CO2 concentrations in the exhaust of a methane-oxygen fueled RDRE. These diagnostics are used to assess the variation in these exhaust thermodynamic properties over a variety of test conditions to assess the effect of varying mass flux, equivalence ratio and propellant mixedness. The wavelength tunability and average output power of DFB lasers are enhanced and optimized for use at MHz rate, extending the utility of the absorption diagnostics to more extreme detonation environments. The optical pressure sensing technique is then demonstrated in laboratory environments and uncertainties are rigorously quantified. Lastly, the CO temperature-sensing technique is extended to extreme temperatures near 10,000 K using a fit of the Boltzmann population fractions across CO energy states. In addition to the presented sensing strategies, a DFB-laser tuning model and comprehensive measurement uncertainty analyses are included in the Appendix to aid in the future design of LAS systems. Additionally, the design and drawings for two facilities used in this work, the UCLA Propulsion Test Platform and Detonation-Impulse Tube, are provided in the Appendix.

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