NASA Wind Tunnel Used to Test Truck Fuel Efficiency

Big trucks are notorious gas guzzlers, but saving the nation as much as $10 billion annually in diesel fuel costs may soon be possible.

Lawrence Livermore National Laboratory (LLNL) has teamed with Navistar Inc., NASA's Ames Research Center, the U.S. Air Force, and industry leaders, to develop and test devices for reducing the aerodynamic drag of tractor-trailers. The devices could increase the trucks' fuel efficiency by as much as 12 percent.

Tractor-trailers use 21 million barrels of fuel per day or about 12 percent of U.S. petroleum consumption. The average fuel mileage of a tractor-trailer is six miles per gallon. At highway speeds, a tractor-trailer uses more than 50 percent of the energy produced by the engine to overcome aerodynamic drag, while rolling resistance consumes roughly 30 percent of the usable energy. A two percent reduction in the aerodynamic drag of tractor-trailers translates into 285 million gallons of diesel fuel saved per year.

LLNL is conducting a full-scale test in the world’s largest wind tunnel, the National Full-Scale Aerodynamics Complex, also known as the NFAC, which operates under the direction of the Arnold Engineering Development Center at Ames. The goal is to identify drag reduction devices, both commercially available and under development, that show the potential for improving fuel efficiency. The wind tunnel test section's huge size, 80 feet by 120 feet, makes it ideal for testing a full-scale semi with a 53-foot trailer.

"We are delighted to host this important test that could help our nation save billions of dollars in fuel costs each year," said S. Pete Worden, director of NASA Ames. "This is an excellent example of what can be accomplished through our collaboration with other federal laboratories and industry."

LLNL computer simulations have identified critical drag producing regions around the trucks, such as the trailer base, the underbody and the gap between tractor and trailer. LLNL scientists estimate that with aerodynamic devices placed in these regions, the trucking industry could see as much as a 20 percent increase in mileage fuel efficiency rate, which saves 4.9 billion gallons of diesel per year, equaling approximately $14.7 billion in diesel fuel savings per year. Prototype devices currently under development will be provided by LLNL and Navistar, which are collaborating to get proven drag reduction devices on the road.

"This is a technology that could easily be installed on the tractor trailer trucks that are out on the highway today," said Kambiz Salari, LLNL’s lead scientist on the project. "And it’s time to market is incredibly quick. In just three years, we could see these devices on the road and realize the real fuel savings."

Livermore's project is funded by the Department of Energy’s Energy Efficiency and Renewable Energy Program’s Freedom Cooperative Automotive Research and fuel partnership. The lab is collaborating with Navistar to push the state-of-the-art in semi-truck aerodynamics and design the next generation of highly aerodynamic, integrated, energy efficient semi-trucks.

Image courtesy of altheengineer