No Longer a Drag: Lab Researchers Boost Truck Fuel Efficiency Through Improved Aerodynamics

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From left: Lawrence Livermore National Laboratory’s Kambiz Salari and Steve Bohlen in front of the Navistar SuperTruck I in the Air Force National Full-Scale Aerodynamics Complex at the NASA Ames Research Center, where the truck will undergo wind tunnel testing to determine fuel savings. Photos by Kate Hunts/LLNL

Lawrence Livermore National Laboratory (LLNL) researchers, as part of aNavistar(link is external) SuperTruck I team, helped design a new type of tractor trailer truck that improves fuel economy by 124 percent, compared to heavy vehicles on the road today.

Seventy-four percent out of 124 percent of this improvement comes from aerodynamic enhancements, while the rest comes from engine efficiency, tire rolling resistance, light weighting and other advancements. On a track test, the new SuperTruck I vehicle achieved 13 mpg, compared to a typical truck on the road that gets around 5.8 mpg.

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Lawrence Livermore and Navistar researchers created SuperTruck I with aerodynamic enhancements, achieving a 124 percent improvement in fuel efficiency, going from 13 mpg, compared to a typical truck on the road that gets around 5.8 mpg. The truck underwent testing at the Air Force NFAC facility National Full-Scale Aerodynamics Complex at the NASA Ames Research Center for wind tunnel testing.

Fuel efficiency improves by 74 percent due to aerodynamic enhancements, equating to 21 billion gallons of diesel fuel saved, 210 million tons of reduced carbon dioxide emissions and $52 billion saved at an average diesel price of $2.51 per gallon annually.

For heavy vehicles, most of the engine’s usable energy goes into overcoming drag and rolling resistance at highway speeds. To combat this problem, the team used computer modeling to demonstrate new aerodynamic body shapes to significantly reduce drag.

Aerodynamic drag is caused from pressure differences around the vehicle — the gap between the tractor and the trailer, the underbody (between the trailer axle and wheels) and the trailer body (base).

“The LLNL Generic Speed Form shape has demonstrated a breakthrough in aerodynamic performance of heavy vehicles,” said Kambiz Salari, a fluid dynamics researcher who heads the project. “We’re not only saving money, we are helping the environment by reducing carbon emissions.”

The LLNL project is part of the Department of Energy(link is external) (DOE) Heavy Vehicle Aerodynamic Drag Consortium R&D, which has led to the advances in fuel economy.

Salari and LLNL’s Jason Ortega, as part of Navistar’s SuperTruck I team, have helped improve the aerodynamic design of the SuperTruck. The truck also has other fuel efficiency improvements, such as a more efficient engine, better rolling resistance, fewer tires and other equipment.

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LLNL researchers used computer modeling to demonstrate new aerodynamic body shapes to reduce drag. Enhancements include reducing the space between the cab and the trailer; panels along the underbody (between the trailer axle and wheels) and back streamline panels.

The team has performed wind tunnel tests at the Air Force National Full-Scale Aerodynamics Complex (NFAC(link is external)) at the NASA Ames Research Center and on-the-road testing using full-scale road conditions. The vehicles could be on the highway as soon as five years.

LLNL is providing guidance to industry to improve the fuel efficiency of class 8 tractor-trailers and tankers through enhanced aerodynamics. Partners for the SuperTruck I effort include Navistar, Wabash National, Bosch, Argonne National Laboratory, Michelin, Mekra Lang, Delco Remy, PPG Industries, Eaton and Sabic Global.

Future plans include: continuing tractor-trailer integration design for radical improvement in aerodynamic drag and fuel economy; continued use of experiments to design a more advanced integrated tractor-trailer; performing scaled experiments to design and validate the performance of aerodynamic add-on devices for integrated tractor-trailers and tankers; investigating fuel economy benefits of truck platooning (similar to a convoy) in collaboration with the National Renewable Energy Laboratory; and continued coordination of industry participation to design the next generation of highly aerodynamic heavy vehicles.