Defense of thesis Marwa Saab

defense of thesis Marwa Saab - laboratory PC2A

Abstract :

The urgent need to transition from fossil fuel combustion to greener energy solutions requires exploring multiple alternatives. Each potential solution comes with its own set of advantages and limitations, making it impractical to rely on a single option. While combustion generates pollutants, its high energy density is essential for many sectors. However, emissions vary depending on the fuel used. In contrast, electrification is often regarded as the cleanest energy option, though it carries high implementation costs and environmental impacts throughout the battery life cycle. This thesis investigates the combustion kinetics of various fuel alternatives, including hydrogen blends, e-fuels, and biofuels in the low to intermediate-temperature range of combustion. Using a rapid compression machine to measure ignition delay times, the study validates newly developed, and evaluates existing kinetic models from the literature. Hydrogen, a carbon-free fuel, is studied as a blend with other fuels regarding its hazard as a highly flammable and explosive gas. The blended fuels consist of C5-chain compounds, each with a different chemical functional group, to assess hydrogen’s influence on each group. The study is done by varying the hydrogen content from 0 to 50 mol% in each fuel mixture and examining these blends under a wide range of conditions: pressures of 20, 15 and 10 bar; stoichiometric and fuel-lean mixtures; in the temperature range of 600–950 K. The fuels studied include n-pentane, 1-pentene, 3-pentanone, and 3-pentanol. Existing models from the literature are tested for the first three fuels, while a new model is developed and validated for 3-pentanol based on IDT and species mole fraction profiles. The same set of experiments was conducted under pressure conditions of 15, 10, and 5 bar at stoichiometric conditions to develop a new kinetic model for tetrahydropyran, a second-generation biofuel. Additionally, IDTs for trimethoxymethane, an e-fuel, were measured under stoichiometric and fuel-lean conditions using the same pressure range. These results were used to test a new model in development and compare it with existing models from the literature. Finally, an ab initio study is performed on alkyl carbonates—key combustible components in lithium batteries—to compute the kinetic rates of H-abstraction reactions by H ̇ and C ̇H3, and their subsequent reactions at the liquid and the gas phase. This thesis contributes to a deeper understanding of the combustion kinetics of promising candidates for alternative energy sources.

Keywords : biofuels,chemical kinetics,combustion,hydrogen