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Hydrocarbon Permeation in Gasoline Vehicle Fuel Systems Using Isobutanol Blends
Journal Article
2012-01-1582
ISSN: 1946-3952, e-ISSN: 1946-3960
Sector:
Topic:
Citation:
Kimura, K., Wolf, L., Baustian, J., and Haskew, H., "Hydrocarbon Permeation in Gasoline Vehicle Fuel Systems Using Isobutanol Blends," SAE Int. J. Fuels Lubr. 5(3):901-927, 2012, https://doi.org/10.4271/2012-01-1582.
Language:
English
Abstract:
In the past decade, a significant market has emerged for
automotive fuels produced from renewable sources. Blends containing
low concentrations of ethanol have been the readily-available
choice for providing renewable content in gasoline fuels.
The simple addition of ethanol to gasoline significantly
increases the mixture's vapor pressure, which can promote
higher vehicle evaporative emissions. Gasoline specifications and
blending practices have been updated to help offset the increase to
vapor pressure and evaporative emissions. However, recent studies
have shown that even at reduced vapor pressure, ethanol can
increase gasoline evaporative emissions by enhancing the permeation
of hydrocarbons through the elastomeric materials found in vehicle
fuel systems.
Technology is currently in development that will allow for the
production of isobutanol from renewable sources. In addition to
high energy density, high octane, and good material compatibility,
isobutanol has low vapor pressure impact when blended with gasoline
and hence, low potential to drive evaporative emissions. However,
until recently the impact of isobutanol to permeation emissions had
not been determined.
A test program was initiated in 2007 to explore the permeation
effects of using isobutanol in gasoline in place of ethanol. The
study compared seven isobutanol and ethanol blends at varying
concentrations while matching fuel properties such as vapor
pressure, aromatics, distillation and oxygen content. Testing was
conducted using fuel systems removed from seven vehicles
representing three technology groups across model years 1981
through 2006. The program duplicated the Coordinated Research
Council (CRC) E-65-3 study protocols which quantified the
permeation impacts of MTBE (Methyl Tertiary Butyl Ether) and
ethanol. The fuel systems were removed from the vehicles and
mounted on custom aluminum frames in positions closely
approximating the vehicle layout. The fuel system rigs were then
exposed to each fuel until the permeation emissions were stable
over a three week average. Permeation emissions were measured in an
emissions test SHED (Sealed Housing for Evaporative Determination)
at 105°F (40.6°C). After stabilization has been determined, the
rigs were placed in a variable temperature SHED (VT-SHED) and
tested on the California two-day diurnal (65°F - 105°F, 18.3°C -
40.6°C) to determine the permeation impact of each fuel. The
results confirm that isobutanol can be used in gasoline with
reduced impact on fuel permeation emissions.