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Browsing by Author "Foust, Thomas, committee member"

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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.
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    Synthesis, properties, and suitability of various oxymethylene ethers for compression ignition fuels
    (Colorado State University. Libraries, 2023) Lucas, Stephen P., author; Windom, Bret, advisor; Foust, Thomas, committee member; Reardon, Kenneth, committee member; Marchese, Anthony J., committee member
    Compression ignition (CI) engines are currently the most common prime mover for medium and heavy duty vehicles; these engines contribute roughly a quarter of US greenhouse gas emissions from transportation, and even higher percentages of particulate and nitrogen oxide emissions. As a result, there have been significant efforts made to reduce these emissions, particularly through selection of low-emissions alternative fuels. Oxymethylene ethers (OMEs) are a class of molecule, typically structured R-O-(CH2O)n-R', which have been considered as a possible blendstock in CI fuels for the goal of soot reduction. Generally, past work has focused on methyl-terminated OMEs, CH3-O-(CH2O)n-CH3, which by virtue of containing no C--C bonds, produce negligible soot. These molecules show significant reductions in soot emission from engines when blended in moderate to high ratios with traditional diesels, however, they have been shown to have inferior physical properties and poor compatibility with some legacy systems. Recent theoretical work has shown that OMEs with non-methyl alkyl groups may have superior performance, albeit at the cost of increased soot formation. In this work, a variety of OMEs with terminating alkyl groups from methyl to butyl are considered for their suitability as CI fuels. The synthesis of these extended OMEs is studied, including formation of n=1 OMEs from common chemical sources, and extension of the chain length to heavier molecules, via reactions over acidic ion exchange resins. Following the synthesis, the properties of these OMEs are studied with respect to their engine applicability. It is found that heavier (propyl- and butyl-terminated) OMEs have superior properties for diesel compatibility, particularly in reactivity, volatility, and water solubility. Extended-alkyl OMEs are found to have higher soot production than methyl-terminated OMEs, but remain superior to diesel soot production on a per-unit-energy basis. A sample of a butyl-terminated OME mixture, n=2-4, is selected as the ideal OME blend for close compatibility with legacy diesel systems. This mixture is blended with certified diesel and tested for ASTM D975 compatibility, passing all required tests but lubricity; decreased heat of combustion is observed but not governed by the diesel standard. Fundamental combustion tests of various mid-weight OMEs are performed in a rapid compression machine, where it is shown that low-temperature chemistry causes a region of decreased dependence of ignition delay on temperature, consistent with methyl-terminated OME behavior. An isopropyl-terminated OME is observed to have low reactivity compared to other OMEs; this fuel is investigated via further rapid compression machine testing and CFR engine testing. It is found that this OME has strong negative-temperature-coefficient ignition behavior - a first for OMEs - and has reactivity lower than other OMEs, but insufficient for direct spark ignition engine testing.