Fundamental Study of Detonation Structure in Rotating Detonation Engine

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The maturation of Brayton-cycle engines has led to a plateau in combustor performance where improvements between successive generations are slight. Detonation-based heat addition, in place of deflagrations, may offer an opportunity to radically improve the performance of both air-breathing and rocket systems. This work is focused on experimentally examining the fundamental flow structures associated with the propagation of a detonation wave in the Rotating Detonation Engine (RDE) configuration to aid in the design and understanding of RDE.

In RDE, one or more detonation waves propagate around the circumference of an annular combustor while reactants are continuously fed axially into the combustor to sustain the detonation wave(s). Numerous applied research activities involving RDE are currently underway to determine how best to integrate RDE in air-breathing and rocket applications. Understanding the complex flowfield of the detonation wave within this combustor has become one of the main challenges in developing RDE.

In this work the propagation of various detonation waves through a flowfield analogous to RDE are studied experimentally. A canonical configuration that “unwraps” the RDE into a linear channel is used to examine the effects of reactant species, mixedness, heat release, and layer height on the structure and propagation characteristics of detonation in RDE. This novel approach allows for the use of high-quality optical measurements such as schlieren, shadowgraph, natural luminescence, and chemiluminescence that reveal previously unseen features of the detonation wave; incomplete reactant mixing produces a number of visually discernible structures. The presence and formation of detonation triple points is directly examined in a variety of reactant compositions; in some cases, the decoupling and decay of detonations occurs if an insufficient number of triple points are present. Results from these experiments are compared to a novel partial mixing model that examines a possible mechanism responsible for experimentally observed waves propagating at a deficit in comparison to the speed predicted by one-dimensional Chapman-Jouguet (CJ) theory. The work presented in this thesis not only yields insight into the design, development, and testing of experimental RDE, but also provides valuable test data for validating numerical simulations of RDE.