Soaring diesel fuel prices and the resulting economic impact on products transported by truck have prompted the Georgia Institute of Technology to dust off and enhance fuel-saving technologies developed during the past decade at the Georgia Tech Research Institute (GTRI). Use of pressurized air “active flow control” techniques combined with conventional aerodynamic streamlining could improve fuel efficiency by 8% to 12% for the heavy trucks used to transport a broad range of products. If installed throughout the U.S. trucking fleet, these technologies for reducing aerodynamic drag could save between 1.6 billion and 2.4 billion gallons of fuel per year, according to GTRI. “The dramatic increase in diesel prices has led the trucking industry to reconsider aerodynamic fuel efficiency improvements that might not have been cost effective only a few years ago,” said Robert Englar, a GTRI principal research engineer. Since diesel prices began their rapid increase, Englar has seen growing interest in the GTRI low-drag active flow control aerodynamic technologies, which were developed with support from the U.S. Department of Energy starting in the late 1990s. He has received numerous inquiries from trucking companies and also railroads, whose higher-speed western track runs could also benefit from aerodynamic drag reduction.Truck designers have reduced aerodynamic drag on the tractor portion of the vehicles by applying streamlining approaches as roof fairings, but those advances have done little to address drag on the boxy aft portion of the trailers. Because only limited streamlining can be done for trailers due to their length, GTRI researchers are adding the active flow control techniques, which use patented pneumatic devices to blow air from slots over small curved aerodynamic surfaces at the rear of the trailers. These air jets smooth the flow of air over the trailers to eliminate air-flow separation, vorticity, and suction on the aft doors, which reduces aerodynamic drag at highway speeds. The renewed research activity is based on aerodynamic research done during the 1980s for applications on U.S. military aircraft. Beyond the fuel savings, the active flow control technology has also been shown to enhance braking and directional control for heavy trucks without using any moving external parts, potentially improving safety. “The next step is to get this into a fleet of trucks for more extensive testing,” Englar said. “At highway speeds, each one percent improvement in fuel economy would result in saving about 200 million gallons of fuel for the U.S. heavy truck fleet. We believe that is worth pursuing.” Go to: EurekAlert

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