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Browsing Theses and Dissertations by Author "Aghahossein Shirazi, Saeid, author"

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    Application of alcohols in spark ignition engines
    (Colorado State University. Libraries, 2018) Aghahossein Shirazi, Saeid, author; Reardon, Kenneth, advisor; Foust, Thomas, committee member; Dandy, David, committee member; Marchese, Anthony, committee member; Windom, Bret, committee member
    Replacing petroleum fuels with sustainable biofuels is a viable option for mitigation of climate change. Alcohols are the most common biofuels worldwide and can be produced biologically from sugary, starchy and lignocellulosic biomass feedstocks. Alcohols are particularly attractive options as fuels for spark ignition engines due to the high octane values of these molecules and their positive influence on performance and emissions. In the context of the US Department of Energy's Co-Optimization of Fuels and Engines (Co-Optima) initiative, a systematic product design methodology was developed to identify alcohols that might be suitable for blending with gasoline for use in spark ignition engines. A detailed database of 943 molecules was established including all possible molecular structures of saturated linear, branched, and cyclic alcohols (C1-C10) with one hydroxyl group. An initial decision framework for removing problematic compounds was devised and applied. Next, the database and decision framework were used to evaluate alcohols suitable for blending in gasoline for spark ignition engines. Three scenarios were considered: (a) low-range (less than 15 vol%) blends with minimal constraints; (b) ideal low-range blends; and (c) high-range (greater than 40 vol%) blends. A dual-alcohol blending approach has been tested. In addition, the azeotropic volatility behavior and mixing/sooting potential of the single and dual-alcohol gasoline blends were studied by monitoring the distillation composition evolution and coupling this with results of a droplet evaporation model. Although nearly all of the work done on alcohol-gasoline blends has been on single-alcohol blends, the results of this study suggest that dual-alcohol blends can overcome many of the limitations of single-alcohol blends to provide a broader spectrum of advantaged properties. A third study focused on the possibility of replacing anhydrous ethanol fuel with hydrous ethanol at the azeotrope composition, which can result in significant energy and cost savings during production. In this collaborative study, the thermophysical properties and evaporation dynamics of a range of hydrous and anhydrous ethanol blends with gasoline were characterized. The results showed that hydrous ethanol blends have the potential to be used in current internal combustion engines as a drop-in fuel with few or no modifications.