Development of a fuel economy model for light-duty and heavy-duty vehicles is
part of the Texas Department of Transportation’s “Estimating Texas Motor Vehicle
Operating Costs” project. A literature review for models that could be used to predict the
fuel economy of light-duty and heavy-duty vehicles resulted in selection of coastdown
coefficients to simulate the combined effects of aerodynamic drag and tire rolling
resistance.
For light-duty vehicles, advantage can be taken of the modeling data provided by
the United States Environmental Protection Agency (EPA) for adjusting chassis
dynamometers to allow accurate determination of emissions and fuel economy so that
compliance with emissions standards and Corporate Average Fuel Economy (CAFE)
regulations can be assessed. Initially, EPA provided vehicle-specific data that were
relevant to a physics-based model of the forces at the tire-road interface. Due to some
limitations of these model parameters, EPA now provides three vehicle-specific
coefficients obtained from vehicle coastdown data. These coefficients can be related
back to the original physics-based model of the forces at the tire-road interface, but not in
a manner that allows the original modeling parameters to be extracted from the
coastdown coefficients. Nevertheless, as long as the operation of a light-duty vehicle
does not involve extreme acceleration or deceleration transients, the coefficients available
from the EPA can be used to accurately predict fuel economy.
Manufacturers of heavy-duty vehicles are not required to meet any sort of CAFE
standards, and the engines used in heavy-duty vehicles, rather than the vehicles
themselves, are tested (using an engine dynamometer) to determine compliance with
emissions standards. Therefore, EPA provides no data that could be useful for predicting
the fuel economy of heavy-duty vehicles. Therefore, it is necessary to perform heavyduty
coastdown tests in order to predict fuel economy, and use these tests to develop
vehicle-specific coefficients for the force at the tire-road interface. Given these
coefficients, the fuel economy of a heavy-duty vehicle can be calculated for any driving
schedule. The heavy-duty vehicle model developed for this project is limited to pre-2007
calendar year heavy-duty vehicles due to the adverse effects of emissions components
that were necessary to comply with emissions standards that went into effect January
2007. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2009-05-80 |
| Date | 03 September 2009 |
| Creators | Ates, Murat |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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