Aerodynamics allow trucks to "fly".

• Position: Transportation

Flow control techniques and aerodynamic improvements developed at the Georgia Institute of Technology, Atlanta, could save the trucking industry hundreds of millions of gallons of fuel per year. Recent tests using a full-size tractor-trailer demonstrate how the techniques--which are based on systems originally developed for jet aircraft wings--could increase fuel economy by as much as 12%. The modifications also could enhance braking and directional control, potentially improving safety for the big rigs.

"Aerodynamically, we have resolved unknowns raised in earlier testing, and the next step is to get this into a fleet of trucks for more extensive testing," says Robert Englar, principal research engineer in the Aerospace, Transportation and Advanced Systems Laboratory of the Georgia Tech Research Institute. "We have shown that this technology now works quite successfully, and we expect that the industry will find a potential 12% fuel economy improvement worth pursuing. At highway speeds, each one percent improvement in fuel economy results in savings of about 200 million gallons of fuel for the U.S. heavy truck fleet."

The aerodynamic improvements produced by geometry changes--which generate fuel savings of as much as six to seven percent--involve rounding aft trailer corners, installing fairings, and making other alterations that smooth air flow over the boxy trailers. Additional savings of five percent come from pneumatic devices that blow air from slots at the rear of the trailer to further improve and prevent separation of air flow.

Before the pneumatic control system can be used widely, however, researchers will have to choose the best source of compressed air for the blowing system, Englar notes. Options include a diesel-powered motor installed in the trailer like current refrigeration units, bleeding pressurized air from the truck's supercharger, or a simple chain drive to turn air blowers from the trailers wheels. Aerodynamic drag becomes dominant only at higher speeds, so the blowing would be turned off when...