Automotive

Electric wind takes truck aerodynamics from brick to slick

Electric wind takes truck aero...
KTH is testing a system the uses electric winds to reduce fuel consumption in trucks
KTH is testing a system the uses electric winds to reduce fuel consumption in trucks
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The KTH system uses plasma actuators mounted on the cab of the truck
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The KTH system uses plasma actuators mounted on the cab of the truck
KTH is testing a system the uses electric winds to reduce fuel consumption in trucks
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KTH is testing a system the uses electric winds to reduce fuel consumption in trucks
KTH researcher Julie Vernet with the model plasma truck
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KTH researcher Julie Vernet with the model plasma truck

Researchers at Sweden's KTH Royal Institute of Technology are developing a device that increases the fuel efficiency of trucks by cloaking them in electric wind. Using plasma actuators to charge the air, the new technology controls the flow of wind around the truck to reduce drag and could improve fuel consumption by five percent.

According to the American Trucking Association, 70 percent of heavy freight in the US alone is moved by trucks – that's 10.5 billion tons of cargo on 3.4 million heavy-duty Class 8 trucks. Worldwide, that not only translates to a lot of stuff hauled by a lot of trucks, but also a lot of fuel burned.

The basic truck is a moving crate that's about as aerodynamic as a brick. As it travels down the highway, it doesn't so much slide through the air as rip it up and fling it churning to the side, which is one reason why passing a juggernaut in the pouring rain is such an unpleasant, if not frightening, experience.

KTH researcher Julie Vernet with the model plasma truck
KTH researcher Julie Vernet with the model plasma truck

Engineers have been aware of this shortcoming since the 1920s and have developed any number of ways of streamlining trucks to make them more aerodynamic. This makes them faster and more stable, as well as more fuel efficient. However, there's still a long way to go, so KTH is taking a page from aerospace engineering.

Aircraft, too, have problems with drag. When a plane is taking off, for example, the increasing angle of attack causes the air to flow less smoothly over the top of the wing and breaks up into turbulence. Engineers get around this by fitting winglets to the tips of the wings to generate vortices that increase lift. KTH wanted something similar for trucks to reduce drag. The snag is that trucks, obviously, aren't airplanes.

What the KTH team came up with is a way to generate vortices at the front of the truck cab to control air flow, but instead of using metal vortex generators like winglets, they used electric wind.

The KTH system uses plasma actuators mounted on the cab of the truck
The KTH system uses plasma actuators mounted on the cab of the truck

The idea is that as air strikes the front of the truck, it flows around it, forming a boundary layer that, if the truck is aerodynamic enough, follows the surface cab and cargo area until it reaches the back and breaks up into eddies. If the truck is moving through still air, that's okay, but if there's wind striking the vehicle at an angle, it can slow down the boundary layer, causing it to separate and form turbulence.

The KTH system uses plasma actuators on the front of the cab. These are two high-voltage electrodes that ionize the surrounding air molecules and accelerates them through the electric field to generate wind without the need for moving parts or protruding airfoils. In addition, these actuators can be adjusted to counter the specific strength and direction of an incoming wind by setting up vortices that force the air into the boundary layer, lowering drag.

"Our ultimate goal is to reduce the flow separation that occurs on the front corners of the truck," says KTH researcher Julie Vernet. "By adding momentum close to the surface, the size of the separated region is reduced."

The video below illustrates how minimizing cross winds on trucks increases efficiency.

Source: KTH

Electric wind vortex generator reduces drag on trucks

10 comments
Bob Stuart
I believe you have confused Whitcomb winglets with vortex generators. The former are on wingtips, resisting the vortex produced by lift. Their effect is very much like a longer wing, but without the extra clearance needed around the airport. A vortex generator can be golf-ball dimples, or lines of small fins, or other schemes intended to thicken and slow a turbulent boundary layer so it can get around a corner without separating. Can this device keep flow attached by attraction, or just affect lateral flow?
DFrancis
If rounded corners, or other passive designs, alone are not sufficient, it makes sense to try an active system. [BTW: The video refers to trucks emitting nitrous oxide (N2O), which is also known as laughing gas. Surely what they mean is nitrogen oxides (NOx).]
jerryd
I agree with Bob S, they are not using terms right as vortexes are drag. Wingtip foils are made to stop vortexes/drag, not make them.
Bob Flint
Assuming it takes less energy than it claims to save, could this be similar to the air bubbles on ships hulls to improve flow and reduce drag?
Don Duncan
Is the 5% savings after subtracting the energy used? I would have liked a breakdown (formula) on cost/gross savings=net. The yearly deaths caused by our highway system's poor design is not found in the MSM. Mixing trucks/cars is dangerous and unnecessary. But then, letting the public sector do what the private sector should be doing is always dangerous and unnecessary. This destructive practice will continue until the superstitious myth that govt. protects is debunked. But the public (govt.) schools will promote the myth for control/exploitation, so the 'net is our only hope, with the exception of home/un-schooling.
Stephen N Russell
See Luigi Colani 80s designs, still valid for truckers these days. Needed.
ljaques
I have the idea someone used Google translate from Svedish for this article. Love the idea of plasma bug zappers to prevent bugs on the windshield, though. Someone should turn it into a video game or sumpin'.
SaysMe
Freakn hilarious, engineers knew problem from 1920's, and still make moving bricks...
anthony88
A truck that breaks wind? I hope they don't use their air horn in built up areas.
Gregg Eshelman
Very few COE (Cab Over Engine) semi tractors are in use in the USA. They fell out of favor as overall length restrictions in several major cities were relaxed or eliminated. Freightliner withdrew their Argosy model from the north American market after 2006 but still makes cabovers for export. Then the Kenworth T600 was introduced, one of the first aerodynamic semi tractors. Take-up by the industry was slow until one major trucking company in the southeast replaced its entire motley fleet with new T600s. It wasn't just for fuel savings. It also saved on maintenance costs, firstly because all new tractors would go a long time before needing major work, secondly because the company would no longer need to stock a wide variety of parts like air filters, brake components etc. for various brands and models of tractors. But before the T600 there was the Peterbilt 372 COE. Its then very unconventional rounded front and integrated deflector atop the cab didn't gain many fans in the tradition bound trucking industry when introduced in 1988 - despite it being able to get over 10 MPG. The 372 was discontinued in 1993. If someone wants to improve the efficiency of a COE tractor, they should start with a Peterbilt 372. Give it flush headlamps, curve and flush mount the grille. Give it a curved windshield and get rid of the overhanging visor. Looking at photos, there are other things that poke out, like the front corner marker lamps, which could be made flush mounted. Then give it a drivetrain with the latest technology.