Ethanol
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The Brazilian flex technology avoided the need for an additional dedicated
sensor to monitor the ethanol–gasoline mix as earlier FFVs were too expensive. The Brazilians used a lambda probe to measure the oxygen concentration in the exhaust as an indirect means to determine the AFR of the blend
being combusted. The results were communicated to the engine control unit
(ECU) to optimize the engine management. The software developed and
commercialized by the Brazilian engineers was called Software Fuel Sensor
(www.wikipedia.com).
5.7 Ethanol Materials Compatibility
Ethanol blended fuels are used in on-road as well as off-road vehicles in
two-or four-stroke engines. In most of the four-stroke engines, fuel is introduced in the intake manifold. Thus, ethanol fuel comes in contact with the
fuel tank, the fuel delivery system, and the engine cylinder. Soft metals such
as zinc, brass, or aluminum, which are commonly found in conventional fuel
storage and dispensing systems, are not compatible with ethanol, especially
at the higher concentration found in E85 motor fuel. Most automotive manufacturers prefer aluminum for the fuel delivery system in order to reduce
the total weight of the vehicle. Earlier older vehicles use lead coated steel
tanks for fuel storage. Ethanol blends will react with such materials and partially dissolve them in the fuel. The dissolved materials clog the fuel filter
and injectors and thus affect performance and drivability. Aluminum can be
safely used if it is hard anodized or nickel plated. Hence, current automobile
storage tanks are made of polymer compounds that are resistant to ethanol
blends. Moreover, stainless steel and bronze material can be used for fuel
delivery systems (Davis 2006). Copper, brass, and bronze also exhibit very
little corrosion with the alcohols.
Nonmetallic materials such as natural rubber, polyurethane, adhesives
(used in older fiberglass piping), certain elastomers, and polymers used in
flex piping. Bushings, gaskets, meters, filters, and materials made of cork also
degrade when in contact with ethanol. Nonmetallic materials that are resistant to ethanol blends include thermosetting reinforced fiber glass, thermoplastic piping, neoprene rubber, polypropylene, vitol, and teflon.
The corrosiveness of alcohols may be influenced by the presence of water,
carbon dioxide, and oxygen. The carbon dioxide and oxygen are more soluble in methanol and ethanol than water, thus increases the risk of corrosion.
Ethanol blends well with gasoline, but it also is completely miscible (mixable) in water. When water infiltrates a tank through sump covers and loose
fittings at the top of the tank, the ethanol in the ethanol–gasoline blend
will absorb the water. Water mixes easier with ethanol than gasoline and
separates from the gasoline. Because of phase separation, the blends in the
161
The Brazilian flex technology avoided the need for an additional dedicated
sensor to monitor the ethanol–gasoline mix as earlier FFVs were too expensive. The Brazilians used a lambda probe to measure the oxygen concentration in the exhaust as an indirect means to determine the AFR of the blend
being combusted. The results were communicated to the engine control unit
(ECU) to optimize the engine management. The software developed and
commercialized by the Brazilian engineers was called Software Fuel Sensor
(www.wikipedia.com).
5.7 Ethanol Materials Compatibility
Ethanol blended fuels are used in on-road as well as off-road vehicles in
two-or four-stroke engines. In most of the four-stroke engines, fuel is introduced in the intake manifold. Thus, ethanol fuel comes in contact with the
fuel tank, the fuel delivery system, and the engine cylinder. Soft metals such
as zinc, brass, or aluminum, which are commonly found in conventional fuel
storage and dispensing systems, are not compatible with ethanol, especially
at the higher concentration found in E85 motor fuel. Most automotive manufacturers prefer aluminum for the fuel delivery system in order to reduce
the total weight of the vehicle. Earlier older vehicles use lead coated steel
tanks for fuel storage. Ethanol blends will react with such materials and partially dissolve them in the fuel. The dissolved materials clog the fuel filter
and injectors and thus affect performance and drivability. Aluminum can be
safely used if it is hard anodized or nickel plated. Hence, current automobile
storage tanks are made of polymer compounds that are resistant to ethanol
blends. Moreover, stainless steel and bronze material can be used for fuel
delivery systems (Davis 2006). Copper, brass, and bronze also exhibit very
little corrosion with the alcohols.
Nonmetallic materials such as natural rubber, polyurethane, adhesives
(used in older fiberglass piping), certain elastomers, and polymers used in
flex piping. Bushings, gaskets, meters, filters, and materials made of cork also
degrade when in contact with ethanol. Nonmetallic materials that are resistant to ethanol blends include thermosetting reinforced fiber glass, thermoplastic piping, neoprene rubber, polypropylene, vitol, and teflon.
The corrosiveness of alcohols may be influenced by the presence of water,
carbon dioxide, and oxygen. The carbon dioxide and oxygen are more soluble in methanol and ethanol than water, thus increases the risk of corrosion.
Ethanol blends well with gasoline, but it also is completely miscible (mixable) in water. When water infiltrates a tank through sump covers and loose
fittings at the top of the tank, the ethanol in the ethanol–gasoline blend
will absorb the water. Water mixes easier with ethanol than gasoline and
separates from the gasoline. Because of phase separation, the blends in the