Date of Award

August 2018

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical and Aerospace Engineering


Ben Akih-Kumgeh

Subject Categories



This thesis focuses on the experimental characterization of the combustion properties of representative alternative fuels. Specifically, a shock tube and direct laser absorption systems are used to investigate the ignition and pyrolysis processes of target fuels. The research problem is motivated by concern about climate change and diminishing fossil fuels. There is a need to develop advanced combustion systems and use more alternative fuels. Innovative designs of combustion systems characterized by lower emissions and higher efficiencies can be facilitated by validated models of the chemical processes involved in combustion. The development of such validated models relies on extensive experimental measurements of various fundamental combustion properties.

The measured properties are global chemical times and species time-histories. For the global times, ignition is characterized by ignition delay time. A novel approach is developed to define pyrolysis time. The chemical reactions that control pyrolysis are generally also included in oxidation processes such as ignition. Pyrolysis is therefore a limiting case that can be used to isolate and test the model subset that is controlled by non-oxidative kinetics. Comparing ignition delay times and pyrolysis times at similar thermodynamic conditions brings out the competition between non-oxidative and oxidative kinetics. The species time-histories of fuel and CO are measured using direct absorption of mid-IR laser.

The target fuels are representative alternative fuels and some less characterized fossil fuel components. Among the alternative fuels studied are furans (2-methyl furan and 2-methyl tetrahydrofuran), alcohols (propanol isomers), and other relevant oxygenated fuels (methyl tert-butyl ether, methyl propanoate). The fossil fuel components are 1,3-dimethylcyclohexane and methane. Methane and methyl propanoate blends are studied to establish the ability of biodiesel to enhance the ignition of methane. Global kinetic times are measured and used for model validation as well as establishing relative reactivity trends.

For the species time-histories, fuel time-histories of 2-methyl tetrahydrofuran and 1,3-dimethylcyclohexane are measured using mid-IR laser around 3.9 µm, associated with C–H bond stretching activities . CO time-histories during pyrolysis of propanol isomers, methyl tert-butyl ether, 2-methyl tetrahydrofuran, methyl propanoate and its blend with methane are obtained through mid-IR ro-vibrational absorption activities around 4.6 µm using Quantum Cascade Laser (QCL).

These measurements of ignition times, pyrolysis times, fuel and CO time-histories provide useful kinetic datasets for validation, refinement, and development of chemical kinetic modelsof selected fuels. The datasets also establish insightful relative reactivity trends for whichchemical explanations are advanced.


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