Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Aerospace Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Liwei Zhang
Abstract
This research investigates the physics of detonation waves and their application to detonation engines, with two primary objectives: (1) to characterize detonation wave propagation, specifically detonation speed and wavefront thickness, in stoichiometric propane-oxygen mixtures near quenching conditions, and (2) to examine the physiochemical processes during propellant injection under detonation engine conditions, focusing on flush-wall-mounted, fluidic-valve injectors.
A multi-fidelity computational approach was employed. Reduced-order modeling based on the Chapman–Jouguet and Zeldovich–von Neumann–Doring models were used to evaluate detonation parameters and select an appropriate chemical mechanism. High-fidelity, multi-dimensional simulations solved the unsteady, compressible, reacting flows with finite-rate chemistry, using Reynolds-Averaged Navier–Stokes equations and the k–ω shear stress transport model. Finite volume approach was employed in the density-based solver. Spatial discretization was carried out using the second-order upwind scheme, and temporal integration utilized the fourth-order Runge–Kutta method. Adaptive mesh refinement was used to improve computational efficiency, and parallelization was implemented using the Intel Message Passing Interface.
Chapters 5 and 6 provide a comprehensive computational investigation of steady and unsteady detonation propagation in stoichiometric propane-oxygen mixtures, focusing on the influence of initial pressure and geometric confinement near the propagation limits. The study examines multidimensional wavefront dynamics, cellular structure evolution, and local extinction–reinitiation phenomena across both regimes. For steady propagation, simulations revealed globally overdriven waves with local wave speeds ranging from 0.7 DCJ to 1.6DCJ and detonation wave thicknesses from 2.8 m to over 150 m. Constrained geometries produced smaller, diverging cells, reinforced by repeated shock–wall interactions. In contrast, unsteady propagation at reduced pressures (10 and 15 kPa) exhibited stuttering and galloping modes, characterized by intermittent reaction, wavefront collapse, and transverse wave reflections. Lower pressures produced longer periods of reaction-shock decoupling and local extinction, particularly in centerline regions, while near-wall zones provided stabilizing effects. Detonation thickness in centerline zones varied stochastically with local speed, whereas wall-adjacent regions showed a monotonic increase in thickness with decreasing speed. Spectral analysis of local wave speeds revealed dominant frequencies linked to triple point dynamics and anisotropic propagation. A comparative summary highlighted that wavelet interactions dominate steady regimes, whereas wall interactions and shock reflections govern unsteady behavior. These findings elucidate the coupled roles of initial pressure and confinement in determining detonation stability and mode transitions, offering new insights into detonation physics near the quenching limit.
Chapter 7 examines detonation wave interactions with a fluidic-valve injector featuring a recessed cavity, using hydrogen-oxygen mixtures. Three cases (I, II, and III) were analyzed, each representing different combinations of initial injector conditions and fuel supply setups. In all cases, a detonation wave was initiated near the headend of the detonation tube. It propagated through the initial section of the tube and underwent diffraction and deformation at the flush-wall orifice. Among the considered cases, Case III, featuring a pre-pressurized initial injector flowfield and a total-pressure-inlet boundary, demonstrated the best agreement with the experimental results. It revealed a strong interaction between the longitudinally traveling detonation wave and the transverse propellant plume expanding from the orifice, causing the detonation wave to bifurcate. One part of the wave continued within the tube, while the other diffracted into the injector, creating a recirculation zone via baroclinic effects. Shock waves propagated within the injector and reflected at the cavity base, generating pressure spikes consistent with experimental observations. The contact surface between the burnt products and fresh propellant penetrated only a short distance into the injector, suggesting a brief interruption time and rapid recovery of the propellant supply. These findings provide insight for injector design in rotating detonation engines.
Keywords
Detonation, Computational fluid dynamics, Combustion, Propagation, Propellant injectors
Disciplines
Aerodynamics and Fluid Mechanics | Other Aerospace Engineering | Propulsion and Power
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Small, Jayson C., "COMPUTATIONAL STUDY OF DETONATION WAVE PROPAGATION AND PROPELLANT INJECTION IN DETONATION ENGINES" (2025). Mechanical and Aerospace Engineering Dissertations. 437.
https://mavmatrix.uta.edu/mechaerospace_dissertations/437
Included in
Aerodynamics and Fluid Mechanics Commons, Other Aerospace Engineering Commons, Propulsion and Power Commons