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Project at a Glance

Title: Fuel efficient active flow control for tractor trailers

Principal Investigator / Author(s): Smith, Andrew

Contractor: ATDynamics, Inc.

Contract Number: ICAT 08-1

Research Program Area: Emissions Monitoring & Control

Topic Areas: Agriculture, ICAT Grants / Technology, Mobile Sources & Fuels


The purpose of this project was to explore the commercial feasibility of two separate Active Flow Control (AFC) technologies and compare them to passive aerodynamic drag-reducing technologies verified by the EPA SmartWay Technology Program. At highway speeds aerodynamic drag accounts for more than half of the fuel consumed by a modern tractor trailer, and any device that can reduce this drag has significant market potential. AFC works by pressurizing the low-pressure vortex, or vacuum, that develops behind a box-shaped trailer as it moves forward; in aerodynamic terms, AFC delays boundary layer separation, reducing the intensity with which the vacuum inhibits the trailer's forward motion. AFC has been proven to reduce aerodynamic drag in the lab and in some aeronautical applications, but has never been developed to full-scale in the freight industry.

Testing was performed per SAE J1321 test procedure and included passive devices for comparison. These commercially available devices included skirt fairings and a trailer tail which reduce turbulence and improve trailer aerodynamics. The final results of the testing indicated that one AFC technology is superior to the other but with no net drag reduction. By comparison, the passive devices showed significant drag reduction, consistently improving fuel economy by 9% or more. It was concluded that passive aerodynamic equipment presently remains the best option to deliver maximum fuel savings to the trucking industry. AFC technology will require further research and development before it can be commercialized.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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