Spectroscopic measurements and modeling of carbonaceous particle combustion in a shock tube

Carbonaceous nanoparticle (CNP) combustion shapes optical signatures and heat release in detonation-relevant multiphase flows, yet quantitative constraints on particle temperature, sublimation rates, reaction kinetics, and wavelength-dependent optical properties remain limited under short-duration, high-temperature and pressure conditions. This dissertation integrates new shock-tube diagnostics with physics-based models to quantify CNP combustion across free-molecular to transitional heat-transfer regimes. These advances deliver actionable constraints for multiphase detonation models by linking measured optical signatures to underlying particle dynamics in extreme multiphase environments. Single color diffuse-backlit extinction imaging (DBI-EI) is used for inferring mass loss rates from optical signature decays. For resolving wavelength dependent optical efficiencies, DBI-EI is developed further by combining a supercontinuum source and an imaging spectrograph, extending classical back-illumination from one/two-color to dense spectral coverage while maintaining robustness to beam steering. The optical efficiencies feed into broadband emission measurements for inferring particle temperature. Complementary gas-phase absorption of diatomic carbon (2) is implemented by targeting the Swan bands with broadband direct absorption, enabling temperature and number-density retrievals during CNP sublimation. Together, these measurements yield time-resolved optical signatures for inferring CNP dynamics behind reflected shocks over a range of pressures and temperatures representative of post-detonation environments. Comparisons with physics-based models are performed by applying current laser-induced incandescence and multiphase flow models, which couple particle optical signatures to energy- and mass-balance equations. Models reproduce observed trends across varying temperature and pressure conditions, although they tend to overpredict the absolute magnitude of ablation rates in all conditions. The model-measurement comparisons provide insight and anchors for improving current multiphase combustion modeling in the dilute limit.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Willhardt, Colton Dean

Contributors dc:contributor

• Glumac, Nick
• Lee, Tonghun
• Brewster, M Quinn
• Panerai, Francesco

• carbon
• soot
• diamond
• spectroscopy
• laser absorption spectroscopy
• emission spectroscopy
• pyrometry
• sublimation
• oxidation
• shock tube
• high temperature
• high pressure
• multiphase

Statement dc:rights

• Copyright 2025 Colton Willhardt

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132549

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132549