Tractor trailers lose valuable miles per gallon to the drag that air exerts, but air may also help tame the fuel guzzling forces. Scientists at Georgia Tech's Research Institute are creating a "circulation control system" that blows a steady current of air around the back of the truck to help boost fuel efficiency. Trailers are an aerodynamic nightmare, essentially boxes on wheels that can't be rounded off because that would cost valuable cargo space. As they plow down the road, getting 7 miles per gallon when they're lucky, wind funneling over the box creates a suction effect that drags down the vehicle.

Robert Englar, a Georgia Tech researcher, called the vortex an "aerodynamic anchor."

Englar, who helped develop air stabilizers working for Lockheed Martin, decided to apply some of the same principles to big rigs. He connects curved bumpers at a truck's back end to a blower that pushes a steady stream of air through them and out the sides. That air flow reduces drag by replacing it with a positive pressure that helps propel the vehicle.

On a test track, Englar's system reduced drag by 32 percent and increased fuel efficiency by 12 percent. That means a truck that once would get 5 miles per gallon gets 5.6 miles per gallon. That marginal increase could save thousands of dollars a year in fuel for a single truck.

"If you look at the poor guy putting $1,200 of diesel fuel in his gas tank, some would give their right arm for a 12 percent increase (in efficiency)," Englar said.

He hopes to bring the gadget's cost below $1,000 over the next few years and some day to include safety features, such as sensors to trigger the air flow to reverse when a driver starts to brake or push against threatening wind gusts.

It's one of few efforts to help trailers as well as tractors reduce wind drag.

"The tractors got smart," said Englar. "The trailers didn't."

With Englar's work, that could soon change.

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On the Net:

http://www.gtri.gatech.edu/

Written By GREG BLUESTEIN

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