Fuel Decomposition and Aromatic Formation Pathways for the Hydrocarbons Contained in Liquid Combustion Fuels

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CTS-0457452 AWARD ABSTRACTFUEL DECOMPOSITION AND AROMATIC FORMATION PATHWAYS FOR THE HYDROCARBONS CONTAINED IN LIQUID COMBUSTION FUELSSoot nanoparticle and aromatic hydrocarbon emissions from combustors are harmful to the global environment and pose public health risks. An understanding of the chemical mechanisms of fuel decomposition and aromatic hydrocarbon formation in flames is important for a rational approach to reduce these emissions. Although such chemistry has been studied extensively for small hydrocarbons, little is known for the larger hydrocarbons that constitute most liquid combustion fuels. This proposal presents a novel approach, based on experimental measurements in flames where a small amount of the species to be studied is added to a well characterized methane flame. This allows the chemistry of these large hydrocarbons to be studied directly. In earlier work we validated this methodology and applied it to C5 to C7 hydrocarbons; the results showed that i) large hydrocarbons can access pathways not available to the well-studied smaller hydrocarbons and ii) these pathways can control soot nanoparticle production. The goal of this proposed research is to elucidate fuel decomposition and aromatic hydrocarbon formation for hydrocarbons present in typical liquid fuels. Our chemical species measurement techniques are rapid and on-line so detailed species maps can be obtained for a wide range of fuel components in a reasonable time. This wide range of data allows us to exploit the differences in the species profiles in developing reaction mechanism tests. Results will be analyzed by extracting decomposition rates from the dopant profiles, examining the correlation between aromatics and their possible precursors, and by computational simulation. Broader Impact: Our work sets the stage for cleaner engine design by expanding the database for the chemical reactivity of large hydrocarbons and by providing rational correlation and extrapolation data for the effect of fuel structure on reactivity. We have provided detailed experimental results from our current studies to numerous groups around the world who have used them to test computational models. The databases generated during the proposed research will be available for direct downloading over the internet. The conclusions from this analysis will facilitate the development of quantitative computer models that can predict nanoparticle formation in practical combustors and of strategies for reducing soot emissions from practical combustors. Undergraduate students have been a key component in our research and will perform course laboratory modules related to this project.