Date of Award

Summer 2019

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Sang Hee Won

Abstract

Cycloalkanes are one type of hydrocarbons present in real jet fuels. The distinct cyclic structure of the cyclo-alkanes impacts the chemical kinetic behavior differently compared to n- and iso-alkanes. At high temperatures, thermal decomposition reactions dominate, producing n-alkyl radicals similar to the oxidation reactions of n-alkanes thus promoting the reactivity. Whereas in low temperatures, the presence of the ring structure essentially suppresses the formation of alkylhydroperoxy radicals (QOOH) from alkylperoxy radicals (RO2), thus exhibiting similar reactivity to iso-alkanes. In previous generations of surrogate fuels, the cyclo-alkane functional group were largely ignored due to low levels of cycloalkanes in traditional jet fuels and their ability to successfully model its characteristics. Cyclo-alkanes have come into renewed interests with their larger presence in alternative jet fuels and the potential of better endothermic performance in high-performance jet fuels (JP-10). Increasing the fraction of cyclo-alkanes in real fuels could create issues in surrogate fuels correctly predicting the chemical functionalities of real fuels with an ever increase fraction of cyclo-alkanes being present. The ignition characteristics of cyclo-alkanes and their mixtures with other molecular classes are investigated by measuring DCN values from an Ignition Quality Tester (IQT). To quantify the role(s) of cyclo-alkane functionality, chemical functional group approach is used by separately defining the CH2 groups in cylco- and n-alkanes and a quantitative structureproperty relationship (QSPR) regression model is constructed based on chemical functional group descriptor against the DCN measurement database. A feature sensitivity analyses are performed to identify relative significance of cyclo-CH2 functional group in autoignition propensity of multi-component fuels by varying the cyclo-alkane fractions.

Rights

© 2019, Dalton Odell Carpenter

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