ORCID

https://orcid.org/0000-0002-9839-126X

Keywords

Hypersonic, Shock, Droplet, Atomization, Breakup, Evaporation

Abstract

The enhanced efficiency of pressure-gain combustion through detonation has fueled renewed research towards how liquid droplets atomize within a hypersonic shock-driven flow field. The heightened energy of post-hypersonic-shock flow compared to post-supersonic-shock flow leads to increased heating of the droplet, and faster phase change rate, which could potentially alter dominant breakup modes from mass loss via aerodynamic drag towards evaporation. As such, the displacement, deformation, and breakup timescales of various micron-scale liquid fuel droplets (RP-2, Jet A-1, and dodecane) behind hypersonic shocks were observed via high-speed 5 MHz shadowgraph imaging. The role of aerodynamic drag was quantified by modulating the shock Mach number (Mach 5.2-6.2), droplet size (42-206 µm), and initial pressure (0.138-1.013 Bar), whereas the deformation geometry was characterized via a surface tension sweep of various liquids (0.023-0.072 N/m). From the Mach and droplet size sweep experiments, breakup times were found to collapse to a linear dimensionless time trend, allowing the use of linear approximation to accurately predict breakup times across a range of hypersonic shock regimes. Furthermore, a breakup predictive model was developed from momentum conservation principles to estimate mass loss of the droplet through time, showing good agreement with experimental breakup time data for droplets over 200 µm in diameter, and across literature. Lastly, the derived breakup trends were compared to evaporation times for single droplets and droplet clouds, with Mie scatter analysis showing considerable lag in the measured evaporation time for an 8 µm cloud of dodecane droplets, when compared to single droplets of equivalent diameter.

Completion Date

2025

Semester

Spring

Committee Chair

Kareem, Ahmed

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Identifier

DP0029387

Document Type

Dissertation/Thesis

Campus Location

Orlando (Main) Campus

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