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B. Geringer, P. Hofmann, R. List:
"Improvements of SI Engine Operation Using Gasoline-Ethanol Blends";
Talk: 11th European Automotive Congress, Budapest (invited); 2007-05-30 - 2007-06-01; in: "Automobile for the Future", EAEC 2007, 11th European Automotive Congress, EAEC 2007 (2007), 195 - 207.

International conventions for climate protection such as the Kyoto Protocol are currently advising the use of renewable primary products for the fuel production in order to reduce the carbon dioxide emissions. Furthermore, the EU directive 2003/30/EG is arranging for the production of biomass fuels and other renewable fuels (5.75% until the year 2010) as a substitute for gasoline and diesel fuels in road traffic. These arrangements lead to a greater independence of fossil energy carriers.
In the case of SI-engines, bio-ethanol is blended to gasoline. In some countries such as Sweden and the United States so-called flex-fuels vehicles have been on the market for a while, which may be operated with mixture rates up to 85% ethanol. In Brazil, on the other hand, this alcohol is even offered and used as a pure biomass fuel.
Ethanol has a calorific value that is 35% lower than that of gasoline which is the reason for the higher fuel demand in the engine operation. At the same time, higher octane numbers lead to a lower knocking tendency and a higher heat of vaporization to an improved cylinder charge. Due to the oxygen bond in the chemical structure of this bio-fuel the combustion is accelerated. The faster conversion of energy as well as the higher possible compression ratio is positively affecting the engine efficiency.
In the course of research work at the Vienna University of Technology gasoline-ethanol blends in the engine operation were tested. At full load neat ethanol showed a significant increase of torque and performance over the whole speed range. In the untreated emissions a strong lowering could be detected in carbon monoxide and unburnt hydrocarbons.

alternative fuels, ethanol, engine efficiency