160
Alternative Fuels for Transportation
failed because of a possible chemical corrosion effect and there was heavy
wear and signs of erosion in the fuel injectors.
5.6 Flexible Fuel Vehicles
Brazilian car makers modified gasoline engines to support ethanol characteristics and changes included compression ratio, amount of fuel injected,
replacement of materials that would be corroded by contact with ethanol,
use of colder spark plugs suitable for dissipating heat due to higher flame
temperatures, and an auxiliary cold-start system that injects gasoline from a
small tank in the engine compartment to help starting when cold.
A desire to increase the use of ethanol fuel and a concern that high ethanol concentrations could cause material compatibility problems led to the
development of a new type of vehicle. The flexible fuel vehicle (FFV) can
operate using various blends of alcohol in the range of 0 to 85% ethanol. A
vehicle optimized for burning E85 could have been produced at lower cost
than a FFV. However, the stoichiometric AFR is 9.8 for E85 and 15 for gasoline. These ratios are too far apart to allow an engine optimized for E85 to
run on gasoline. The ability of the FFV to automatically adjust its AFR allows
it to use any combination of gasoline–ethanol blends. Thus, the FFV can run
on gasoline in locations where E85 is not available but helps to reduce the
demand for petroleum fuels where E85 is available.
Automotive manufacturers produced the FFV vehicles compatible with
E85. Further, due to the different AFR mixture requirement of neat gasoline
and E85, the fuel delivery systems are sized to handle the increased volumes
of fuel when using ethanol. Moreover, ethanol is a higher octane fuel and
hence sparks timing is advanced in order to achieve the better engine performance and emissions characteristics. Moreover, since the ethanol has a lower
calorific value fuel compared to gasoline, a higher fuel flow rate is required
to meet the power demand.
The most common commercially available FFV in the market is the ethanol flexible-fuel vehicle, with more than 17 million automobiles and light
duty trucks on the roads around the world by early 2009, and concentrated
in four markets, Brazil (8.2 million), the United States (almost 8 million),
Canada (600,000), and Europe, led by Sweden (311,122). North American and
European FFVs are optimized to run on a maximum blend of 15% gasoline
with 85% anhydrous ethanol (called E85 fuel). The limit to the alcohol content is set to avoid the cold starting problems (www.wikipedia.com).
The possibility of using various blends of gasoline–ethanol in the fuel tank
of FFV vehicles requires means to determine the concentration of ethanol in
the fuel line. Thus, a fuel sensor is provided in the fuel system to measure the
concentration of ethanol in the blend and optimize the engine management
system accordingly.
Alternative Fuels for Transportation
failed because of a possible chemical corrosion effect and there was heavy
wear and signs of erosion in the fuel injectors.
5.6 Flexible Fuel Vehicles
Brazilian car makers modified gasoline engines to support ethanol characteristics and changes included compression ratio, amount of fuel injected,
replacement of materials that would be corroded by contact with ethanol,
use of colder spark plugs suitable for dissipating heat due to higher flame
temperatures, and an auxiliary cold-start system that injects gasoline from a
small tank in the engine compartment to help starting when cold.
A desire to increase the use of ethanol fuel and a concern that high ethanol concentrations could cause material compatibility problems led to the
development of a new type of vehicle. The flexible fuel vehicle (FFV) can
operate using various blends of alcohol in the range of 0 to 85% ethanol. A
vehicle optimized for burning E85 could have been produced at lower cost
than a FFV. However, the stoichiometric AFR is 9.8 for E85 and 15 for gasoline. These ratios are too far apart to allow an engine optimized for E85 to
run on gasoline. The ability of the FFV to automatically adjust its AFR allows
it to use any combination of gasoline–ethanol blends. Thus, the FFV can run
on gasoline in locations where E85 is not available but helps to reduce the
demand for petroleum fuels where E85 is available.
Automotive manufacturers produced the FFV vehicles compatible with
E85. Further, due to the different AFR mixture requirement of neat gasoline
and E85, the fuel delivery systems are sized to handle the increased volumes
of fuel when using ethanol. Moreover, ethanol is a higher octane fuel and
hence sparks timing is advanced in order to achieve the better engine performance and emissions characteristics. Moreover, since the ethanol has a lower
calorific value fuel compared to gasoline, a higher fuel flow rate is required
to meet the power demand.
The most common commercially available FFV in the market is the ethanol flexible-fuel vehicle, with more than 17 million automobiles and light
duty trucks on the roads around the world by early 2009, and concentrated
in four markets, Brazil (8.2 million), the United States (almost 8 million),
Canada (600,000), and Europe, led by Sweden (311,122). North American and
European FFVs are optimized to run on a maximum blend of 15% gasoline
with 85% anhydrous ethanol (called E85 fuel). The limit to the alcohol content is set to avoid the cold starting problems (www.wikipedia.com).
The possibility of using various blends of gasoline–ethanol in the fuel tank
of FFV vehicles requires means to determine the concentration of ethanol in
the fuel line. Thus, a fuel sensor is provided in the fuel system to measure the
concentration of ethanol in the blend and optimize the engine management
system accordingly.