Design and Experimentation of a Premixed Rotating Detonation Engine

Desire for a more efficient air breathing engine has shifted research attention to the Rotating Detonation Engine (RDE). Detonation is a more efficient combustion process than deflagration and provides a pressure gain. The RDE detonation cycle occurs in a compact volume to produce a high specific impulse engine. Computational fluid dynamic (CFD) models have predicted higher specific impulse and detonation wave speeds than has been seen in experimental RDE. The CFD models frequently assume premixed reactants and ignore inlet geometries to facilitate rapid computation. An experimental premixed RDE was sought to test if the premixed assumption in CFD was the root cause of the discrepancy between computational and experimental results. Design of a successful premixed RDE employed a feed system that simultaneously arrested flashback into the premixture while it fed the detonation. Flashback arresting feed designs were explored with single injector tests and validated with a fully premixed RDE. A relationship between arresting length and detonation feed requirements was derived and used to design a premixed RDE that fed premixture through feed slots that were 2.5 cm long and 0.5 mm high and operated on ethylene fuel and air oxidizer. The premixed RDE operated within a narrower region of equivalence ratio than a non-premixed RDE. Chemiluminescence video indicated that the premixed RDE experience combustion reactant-product mixing, and supports the theory that mixing delays are the root cause of slower wave speeds in experimental RDE. Time averaged chemiluminescence results indicate that RDE detonations to not complete the reaction within the detonation wave, and suggest that future CFD studies should assume unmixed reactants, model the full injection geometry, and include a comprehensive chemical mechanism