The work presented herein consist of first studying the instantaneous properties of the detonation waves in a rotating detonation rocket engine by tracking each individual wave and recording its position, velocity, and peak intensity as it travels around the annulus. Results for a steady portion of a test performed on a rotating detonation rocket engine show that the wave properties exhibit oscillatory behavior. Results obtained from the rotating detonation rocket engine show that the properties are highly dependent on the azimuthal position. In an attempt to understanding the cause of such a behavior, similar investigations were performed on an air-breathing rotating detonation engine with a different injection design to see if the behavior persists. Results show that air-breathing rotating detonation engines do indeed exhibit this behavior in a more attenuated fashion. It is demonstrated that the pre-detonation hole might be the reason for the observed combustion instabilities. After establishing the steady state behavior of a single mode in a rotating detonation rocket engine, transient analyses of multiple tests were performed in order to capture the relative wave speeds between the modes. Wave speeds and operational frequency plots showcasing the range of operation of each mode (single and counter-propagating) were constructed. Moreover, operating maps of the engine were built and clearly demonstrate where each mode resides. The mode transition instability phenomenon observed in rotating detonation rocket engines is then studied. Each mode transition is distinguished by different mechanics and behavior requiring different diagnostic tools and research techniques to analyse. In this investigation, five possible mode transitions in rotating detonation engines have been identified and are Types AS, DS, AO, DO and SO and their behavior is discussed. Also, the counter-propagation wave behavior within an intermidiate period for Type _O mode transition have been discussed.


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Graduation Date





Ahmed, Kareem


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Mechanical and Aerospace Engineering

Degree Program

Aerospace Engineering







Release Date

December 2021

Length of Campus-only Access


Access Status

Doctoral Dissertation (Open Access)