Robert J. Englar, GTRI’s principal research engineer, said that wind-tunnel tests of a syetem he has engineered on automobiles have shown that drag can be reduced anywhere from 35% to 50%. For tractor trailers, a 35% reduction would translate into a 12% fuel savings, or about 1.2-billion gallons of diesel per year. A 50% drag reduction would translate into 1.7-billion gallons annually for U.S. heavy-duty truck fleets.
Englar's system, outlined in a paper for the Society of Automotive Engineers entitled “Advanced Aerodynamic Devices to Improve the Performance, Economics, Handling and Safety of Heavy Vehicles,” involves installing patented curves corner-to-corner along the top, bottom and both sides of a trailer.
Compressed air is blown from slots in the trailer along the curves, using pressure coming off the engine's turbocharger to power a pneumatic system. This decreases drag by making the entire trailer act similarly to an airplane’s wing to lift a portion of the truck's weight off the tires. Air blown from the bottom has the opposite effect, putting downward force on the tires to improve braking and traction.
In addition to fuel economy, Englar said his system might also improve safety. Use of blowing slots on each side of the trailer could counter crosswinds, which would help keep drivers from jackknifing.
Road tests will begin late this summer at testing grounds in Ohio, with results expected by this fall.