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Evaluation of ethanol substitution in a compression ignition engine




Van Roekel, Chris, author
Olsen, Daniel B., advisor
Bandhauer, Todd, committee member
Reardon, Ken, committee member

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Heavy duty compression ignition engines rely on advanced emission control strategies to mitigate regulated emissions in compliance with requirements set by the Environmental Protection Agency. These strategies add significant cost and complexity to engine design. Previous work identified that a diesel-ethanol dual fuel combustion technique may be able to reduce diesel fuel consumption and supplement current emission control methods. The substitution of diesel fuel with a renewable, U.S. based fuel such as corn ethanol would also improve US energy security. A review of diesel-ethanol dual fuel combustion identified five possible methods of diesel-ethanol dual fuel combustion. They were ethanol-diesel emulsions, ethanol-diesel-additive blending, twin direct injection of ethanol and diesel, ethanol fumigation of intake air with standard diesel fuel injection, and full substitution of diesel with ethanol. Analysis of ethanol-diesel emulsions and ethanol-diesel-additive blending concluded that only low volumes of ethanol (<10%) could be blended in diesel fuel before the two fuels were immiscible. However, analysis using ternary phase diagrams showed that additives such as B100 biodiesel could be used to extend the substitution limit significantly such that at 25°C mixtures of 80% 200 proof ethanol, 10% B100 biodiesel, and 10% off-road diesel were visibly miscible. Miscible mixtures containing high volumes of ethanol underwent further analysis, which showed that these fuels were not suitable drop in replacements for diesel fuel due to poor cold flow properties. Based on fuel blending analysis and previously published literature ethanol fumigation of intake air was selected for an on-engine demonstration using a Cummins 6.7L QSB Tier 4 Final engine. Three ethanol based fuels were selected for this dual fuel combustion work: 200 proof ethanol, 190 proof ethanol, and a blend of 15% E0 gasoline and 85% 200 proof ethanol. Pre and post aftertreatment emission data and high speed combustion data were collected while operating the engine at ISO 8178 test points C1-7, C1-3, and C2-4. The maximum diesel substitution at each test point was similar among the three test fuels. and at moderate to high engine loads diesel substitution was limited to 25% and 39%, respectively due to engine knock . At low engine loads substitution was limited to 25% by exhaust emission requirements. Premixed ethanol combustion increased brake specific efficiency at moderate and high engine loads by 3% and 3.2%, respectively, but reduced efficiency at low engine loads by 1.4%. Finally, although the complete ISO 8178 test map was not completed the Tier 4 Final after treatment system was able to reduce ethanol premixed combustion emissions to at or below the diesel baseline emissions at nearly every test point.


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dual fuel


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