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Engine Efficiency

The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in
mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30).
A single-cylinder research engine is used with a low and high compression ratio of 9.2:1 and 11.85:1 respectively. The
engine is equipped with hydraulically actuated valves, laboratory intake air, and is capable of external exhaust gas
recirculation (EGR). All fuels are operated to full-load conditions with λ=1, using both 0% and 15% external cooled EGR.
The results demonstrate that higher octane number bio-fuels better utilize higher compression ratios with high
stoichiometric torque capability. Specifically, the unique properties of ethanol enabled a doubling of the stoichiometric
torque capability with the 11.85:1 compression ratio using E30 as compared to 87 AKI, up to 20 bar IMEPg at λ=1 (with
15% EGR, 18.5 bar with 0% EGR). EGR was shown to provide thermodynamic advantages with all fuels. The results
demonstrate that E30 may further the downsizing and downspeeding of engines by achieving increased low speed torque,
even with high compression ratios. The results suggest that at mid-level alcohol-gasoline blends, engine and vehicle
optimization can offset the reduced fuel energy content of alcohol-gasoline blends, and likely reduce vehicle fuel
consumption and tailpipe CO2 emissions.

Publication Date
Contact Email
Contact Person
Tim Theiss
Contact Organization
Oak Ridge National Laboratory
Bioenergy Category
Derek Splitter
Funded from the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office.
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