Pneumatics and aerodynamics could boost tractor-trailer fuel efficiency

Flow-control techniques and aerodynamic improvements developed at the Georgia Institute of Technology could save the U.S. trucking industry hundreds of millions of gallons of fuel annually. The aerodynamic improvements produced by geometry changes, which generate fuel savings of as much as 7%, involve rounding aft trailer corners, installing fairings, and making other changes that smooth airflow over the boxy trailers. Fuel savings of an additional 5% come from pneumatic devices that blow air from slots at the rear of the trailer to further improve and prevent separation of airflow. Recent tests done using a full-size tractor-trailer truck show the techniques could boost fuel economy by as much as 12%. The improvements could also enhance braking and directional control, potentially improving safety for the big vehicles. The tests are based on systems originally developed for jet-aircraft wings. "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," said Robert Englar, principal research engineer in the Aerospace, Transportation and Advanced Systems Laboratory of the Georgia Tech Research Institute (GTRI). Englar's research team worked with Volvo Trucks of North America and Great Dane Trailers, the manufacturers of the basic tractor and trailer, respectively, to install the new aerodynamic features and blowing system at the rear of the trailer. A series of higher-speed test runs at the Transportation Research Center's Ohio fuel-economy test track in September demonstrated the fuel savings that had been expected. The tests involved operating a blowing-equipped test tractor-trailer for several different 45-mile runs around a 7.5-mile oval at highway speeds of 65 and 75 mph. A control truck that did not have the aerodynamic improvements or pneumatic-control system was operated under the same conditions for a comparison. As an additional control, the test truck was