‘Pneumatic truck’ could boost fuel economy up to 25%
Phase-two testing starts this year on a tractor-trailer diesel truck equipped with aerodynamic-assisting air jets, which could slash drag by about 50% and boost fuel economy by up to 25%.
The little jets improve air flow at the trailing edges of trailers, employing successful principles earlier applied to aircraft.
The first phase of experiments on a smaller-scale wind-tunnel model at Georgia Tech Research Institute (see Diesel Fuel News 5/28/01, p2) led to design of a full-scale on-road test vehicle based on a Volvo Truck/Great Dane trailer big-rig combo.
The first vehicle test, sponsored by U.S. Department of Energy (DOE), aimed to determine fuel economy under highway conditions and learn about possible system problems.
The phase-one test version exposed a flaw: A faring designed to reduce drag around the exterior-mounted auxiliary motors and blowers didn’t perform as wind-tunnel testing had indicated. That prompted follow-up tests in the wind tunnel, which led to discovery of an aerodynamic fix.
Phase-two tests later this year will move the blower-motor components inside the trailer to eliminate the faring problem discovered in phase-one.
In a future commercial application, engineering designers probably would put the blower-motors on the trailer face behind the tractor, perhaps integrated into the auxiliary-power refrigeration units used on many trucks today. This not only would eliminate aerodynamic drag and use readily available space, but also would conserve interior trailer space dedicated to revenue freight. Air ducts from the blower could run along the outside-bottom of the trailer — the same available space where spare tires are stored.
Phase-one testing with the earlier design produced only about 5-6% fuel economy improvement in the standard Society of Automotive Engineers (SAE) “Type-II” testing on a 7.5 mile track at Transportation Research Center, in East Liberty, Ohio. These SAE tests followed several “tuning” tests at Volvo facilities in Greensboro, N.C.
The new design — eliminating the faring problem — should increase fuel economy by about 20-25% over the stock tractor-trailer rig, explains Georgia Tech Research Institute (GTRI) engineer Robert Englar.
GTRI, which holds the patents on this system, continues to work with Volvo Trucks and Great Dane trailers for test programs, with funding from DOE and with cooperation from American Trucking Associations.
Greatest fuel economy gains with the pneumatic system probably will be realized for trucks operating long distances at highway speeds over flat terrain, Englar explains. Aside from the Appalachian Ridge, flatter terrain is typical of much of the U.S. highway system east of the Rockies.
The pneumatic system also shows ability to compensate for dangerously strong cross-winds sometimes occurring on highways, and also for boosting drag on downhill slopes in order to improve truck safety and reduce brake-wear.
(Note: A paper describing the system ‘s engineering principles — SAE 2001-01-2072 — just beat out 3,000 other papers for SAE ‘s top “Arch Co/well Merit” award for best technical paper of 2001).
Besides truck application, the system also might help boost fuel economy on larger sport-utility vehicles (SUVs). At Georgia Tech, one such vehicle left over from an earlier SAE “Future Truck” competition has just been converted with a pneumatic system and is starting to undergo wind-tunnel evaluations.
Once system tests are complete and fuel economy benefits verified, then the researchers can begin to estimate cost/payback calculations for vehicle owners. Large fuel economy gains potentially could pay-off the capital cost of the system quickly.
COPYRIGHT 2003 Hart Energy Publishing, LP.
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