Atmospheric Chemistry Program Seminar: Nicole Labbe, CU Mech Eng
Resolving The Complex Chemistry of Combustion
Prof. Nicole Labbe,
CU Mechanical Engineering
"High temperature gas reacting systems are among the most complex chemical kinetics systems to model. For example, a prototypical gas phase reacting system is combustion, where fuels can undergo tens of thousands of unique competing reactions via thousands of unique chemical species. Further complicating the chemistry, these systems can be highly pressure dependent, and even modest pressure fluctuations can drastically change both reaction rate and species distributions. With such large combinatorial possibilities for reactions and product species, theory alone is often unable to fully resolve the chemical mechanism due to computational limitations. Furthermore, the breadth of reactions and species present limits the ability of experiments to fully resolve the chemistry of may gas phase reacting systems. However, through careful combination of both theoretical and experimental techniques, at least the most critical reactions can often be revealed for accurate chemical model development. In this work, we demonstrate how a combined approach using both semi-automated theoretical kinetics and gas phase speciation experiments was used to resolve several kinetics disputes in the literature due to unresolved kinetic mechanisms. First, we demonstrate how theoretical kinetics was the key to clearing up a discrepancy as to the source of methyl ketene in the pyrolysis of a biodiesel component, ethyl propanoate. Next, we show that a new tunable lab-scale VUV light source was able to experimentally prove a theoretically predicted keto-enol tautomerization for acetone for the first time. Finally, we explore how a combined experimental and theoretical approach resolved how the location of the double bond in methylcyclohexene dramatically changes the sooting propensity between each of the three possible isomers."