Detailed Chemical Kinetic Modeling of Biofuels and their Blends with Conventional Fuel Components

Fuel components derived from non-edible biomass are regarded as sustainable substituents for conventional fuels. A major prerequisite for their application in engines, however, is the understanding of their detailed oxidation behavior, which strongly depends on the fuel structure. In the present work, the oxidation behavior of a group of bio-derived furans and tetrahydrofurans is investigated by developing their detailed chemical kinetic mechanisms. Furthermore, to identify potential fuel blends for the desired applications, a systematic optimization approach is proposed.
The first part of this thesis is a detailed investigation of the effect of blending an octane booster, 2-methylfuran, with the more reactive primary reference fuel candidate, n-heptane. A detailed model comprising the chemistry relevant for 2-methylfuran and n-heptane was formulated. The detailed chemical analysis reveals no direct interaction between these two fuels. The second part of the thesis addresses the question, how a small change in molecular structure can lead to a substantial change in the reactivity. The oxidation behavior of two structural isomers, 2-methyltetrahydrofuran and 3-methyltetrahydrofuran, is investigated numerically and experimentally. A comparative reaction path analysis ensures that the location of the side chain is the decisive factor for their ignition propensity. The last part of the thesis focuses on the optimization of potential gasoline blending agents. For this purpose, a large database containing the physical and chemical properties of about 500 fuel components was established. In order to identify the potential candidates, a simple automatics tool was developed. Fuel candidates comprising the alcohol and ketone functional groups were observed to have good potential.