In Brazilian market, Flex-Fuel vehicles represented over 85% of
new light-duty vehicles sold in 2010. These vehicles can use
gasoline blended with anhydrous ethanol (18 to 25% v/v), 100% of
hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any
blend of these fuels.
Some studies regarding Flex-Fuel technology are being made in
Brazil, but there are not many published information about fuel
properties of different ethanol-gasoline blends. Also, it is
important to better understand emissions of aldehydes, unburned
ethanol and total hydrocarbons of different ethanol blends on
gasoline.
A Flex-Fuel engine, 1.4 l, 4 cylinders was tested on a
dynamometer. A FTIR (Fourier Transform Infrared analyzer) bench
measured aldehydes, unburned ethanol and total hydrocarbons. It was
used Gasoline with 25% of anhydrous ethanol was used as a reference
fuel (E25). E25 was blended with different hydrous ethanol contents
such as 30% (H30), 50% (H50), 80% (H80) and 100% (H100). To control
the engine operation, a programmable ECU (Engine Control Unit) was
used, allowing spark timing calibration either for maximum break
torque (MBT) or to keep the engine below the knocking limit.
Operating conditions included partial load with stoichiometric
air-fuel ratio, for three different engine speed conditions. Test
results were handled by the STATISTICA® software that calculated a
95% confidence interval for each operating condition. The main
physical properties of the different blends were analyzed as part
of this work, including H/C and O/C molar ratio, net heating value
and others.
The emissions results presented a reduction trend for CO, NMHC
and NOx, a trend of increase of aldehydes and unburned ethanol and
no significant changes for CO2.