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Iso-Stoichiometric Ternary Blends of Gasoline, Ethanol and Methanol: Investigations into Exhaust Emissions, Blend Properties and Octane Numbers
ISSN: 1946-3952, e-ISSN: 1946-3960
Published September 10, 2012 by SAE International in United States
Citation: Turner, J., Pearson, R., Bell, A., de Goede, S. et al., "Iso-Stoichiometric Ternary Blends of Gasoline, Ethanol and Methanol: Investigations into Exhaust Emissions, Blend Properties and Octane Numbers," SAE Int. J. Fuels Lubr. 5(3):945-967, 2012, https://doi.org/10.4271/2012-01-1586.
Iso-stoichiometric ternary blends - in which three-component blends of gasoline, ethanol and methanol are configured to the same stoichiometric air-fuel ratio as an equivalent binary ethanol-gasoline blend - can function as invisible "drop-in" fuels suitable for the existing E85/gasoline flex-fuel vehicle fleet. This has been demonstrated for the two principal means of detecting alcohol content in such vehicles, which are considered to be a virtual, or software-based, sensor, and a physical sensor in the fuel line. Furthermore when using such fuels the tailpipe CO₂ emissions are essentially identical to those found when the vehicle is operated on E85. Because of the fact that methanol can be made from a wider range of feed stocks than ethanol and at a cheaper price, these blends then provide opportunities to improve energy security, to reduce greenhouse gas emissions and to produce a fuel blend which could potentially be cheaper on a cost-per-unit-energy basis than gasoline or diesel.
The present work extends the validation process for these blends by presenting exhaust emissions measured from a vehicle fitted with a physical alcohol sensor and operated on several ternary blends equivalent to E85. These results show that existing emissions control technology can easily manage exhaust gas aftertreatment when a vehicle is operated on such blends. This is an important finding with regard to their manufacturer and regulatory acceptance.
Also, the impact of the methanol-containing nature of ternary blends was investigated. In order to do this, target ternary blends of gasoline, ethanol and methanol were prepared with the low oxygen content Coordinated European Council (CEC) emissions reference fuel CEC RF-02-03 and results of physicochemical analyses are presented. These include water tolerance, blend stability, thermal and oxidative stability, volatility and density. Nitrile rubber, Viton and silicone rubber seal swell properties are presented and discussed. In order to investigate octane effects, iso-stoichiometric blends equivalent to E15 were prepared and analyzed, and utilizing molar octane blending modeling the expected E85-equivalent blend octane indices can be predicted.
As a result of this work observations are made on air-quality and materials compatibility impacts, and the attractiveness of the approach from a governmental and customer viewpoint.
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