Keywords

Gaseous detonations, Cellular structure, Pressure gain combustion, Oblique detonation wave, Combustion modeling

Abstract

The advent of detonation-based propulsion systems represents an opportunity for more sustainable combustion processes and hypersonic travel. In regular detonations, some yet to be resolved instabilities are attributed to the propagation and collision of triple points, formed at the intersection of a Mach stem, an incident shock and a transverse wave. Over time, the tracks observed by these points form a structure made of diamond-shaped cells. Ultimately, The ability to sustain these instabilities plays a key role in the propagation of detonations. The present work unveils the dynamics of gaseous detonations at a sub-cellular level. The experiments are conducted with hydrogen fuel which is of great potential for detonation engine applications. The hydrogen-oxygen mixtures are held at stoichiometry and the nitrogen dilution in oxygen is varied from 30% to 70%. This allows to observe the effects of activation energy through the dilution on the sub-cellular wave dynamics. Measurements of cell sizes and wave velocity are reported through shadowgraph imaging. A new methodology is developed for the simultaneous resolution of the velocity field and cellular structure. The statistical analysis is made possible due to the design of a fully automated detonation facility. The experiments are conducted in a thin channel to minimize gradients in the third direction and confine the detonation cells to a plane. The results in cell sizes are in good agreement with the literature and expand the conditions reported thus far. Local observations of the velocity within the cells are used to explain the regularity of the overall wave speed, found to increase at lower dilution. Lastly, high fidelity simulations are conducted to model the cellular structure in hydrogen-air oblique detonation waves. Similarly to the experiments, the velocity field is extracted along the detonation cells and reveals the effects of wave curvature on triple point dynamics.

Completion Date

2024

Semester

Summer

Committee Chair

Ahmed, Kareem

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Aerospace Engineering

Format

application/pdf

Release Date

8-15-2027

Length of Campus-only Access

3 years

Access Status

Doctoral Dissertation (Campus-only Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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Restricted to the UCF community until 8-15-2027; it will then be open access.

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