This paper evaluated the use of water-ethanol mixtures as fuel for internal combustion engines. Spark-Ignited (SI) and Homogeneous Charge Compression Ignition (HCCI) operation modes were evaluated. Operation was only kept under the knock limit defined by a Ringing Intensity (RI) parameter. Spark-Ignited operation mode was simulated with a turbulent flame speed combustion model. It could be noticed that as the water fraction increased, higher IMEP values (from 1350 to 1450 MPa) were possible. CO emissions were slightly lower whereas NOx emissions were dramatically reduced due to lower in-cylinder temperatures. Indicated efficiency remained more or less constant at a value of 42% regardless of changes in water fraction. Simulation of HCCI operation was performed for 3 different situations: equivalence ratio of Φ=1, Φ=0.75 and Φ=0.25 and combustion durations of 30°, 20° and 10°, respectively. It was noticed a slight reduction on IMEP with increased water fraction for all cases. Emissions of NOx were overall much reduced in comparison to SI operation and reduced steadily with increased water fraction when on HCCI combustion. For one of the cases (Φ=0.25) values were negligible due to very low in-cylinder temperatures. CO emissions are highly dependent on air/fuel ratio and followed this trend closely. However, for every equivalence ratio, values were lower as water fraction increased. Indicated efficiency with HCCI was shown to be higher than with SI operation for leaner mixtures and reasonably the same when in stoichiometric operation (Φ=1), with values within 42-45%. Increasing water fraction did not show to have any important effect on efficiency, with values remaining soundly constant. All in all it is noticeable that the use of ethanol with high water fractions is a promising alternative to enable the use of a low cost renewable fuel which offers good improvement chances if its properties are properly explored. To promote ignition with high water fractions still remain a challenge that may call for advanced combustion concepts.
Low cost wet ethanol fuel: Benefits and challenges
2012
26 Seiten, 22 Bilder, 37 Quellen
Aufsatz (Konferenz)
Englisch
Low cost wet ethanol fuel: benefits and challenges
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