NFAC aerodynamic truck test to set industry standards

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Industry experts say Class 8 tractor-trailers are responsible for around 12 percent of the total U.S. consumption of petroleum, but to truck drivers, it's the high cost of fuel that has their attention.

William "Billy" Brain, a regional truck driver from middle Tennessee, knows it's mainly the high cost of fuel that eats into his paycheck.

Mike Elliot, his boss and the owner of a small trucking business based in Belvidere, Tenn., said, "It [diesel fuel] comes to about one third of my overall [annual] cost."

Data from an aerodynamic test being conducted on tractor trailers in the world's largest wind tunnel facility in northern California will help address truck drivers' concerns about increased fuel costs on the road.

"The primary goal of this test is to [acquire] baseline on market and near-to-market aerodynamic improvement devices [for tractor trailers]," said Chris Hartley, the Jacobs Technology engineer involved with the project at Arnold Engineering Development Center's National Full-Scale Aerodynamics Complex (NFAC) in Moffett Field, Calif.

The devices he is referring to are drag-reduction components that can be attached to truck beds and trailers to improve the aerodynamics of the vehicle, making for a more fuel efficient ride.

Industry experts say that even a 1 percent fuel efficiency rate would reduce the number of diesel fuel gallons by 245 million annually for the nation. A 1 percent fuel efficiency rate also translates to roughly 3 million tons of CO2 (from emissions) that would not be released into the atmosphere.

The truck test's primary customer, the Department of Energy, has been working on drag-reduction devices for the past seven years.

Prior to this current test, those in the trucking industry had to rely on reports and 'white papers' written by companies on their claims for drag reduction products that would translate to fuel savings, according to Dr. Kambiz Salari, the lead engineer with the Department of Energy's Lawrence Livermore National Lab on the truck test. Dr. Salari said the companies trying to sell these products had no way to back up their claims with independent research.

Dr. Salari said the truck aerodynamic test at NFAC will provide that authoritative assurance by satisfying three objectives.

"The first one is in support of DOE's mission, to provide guidance to industry to improve the fuel economy of Class 8 tractor trailers through the use of aerodynamic drag reduction devices," he said. "Then, the second objective is on behalf of DOE to expand and coordinate industry participation, which leads to significant on-the-road fuel economy and the third is to join with industry, getting devices on the road. And then demonstrate new drag reduction techniques and concepts through use of virtual modeling and testing environments."

Hartley said the Navistar Company has teamed up with the DOE on the current test to establish a baseline on the effectiveness of these drag reduction products.

"In addition to these fairings, which they're designing to test on the trailers themselves, they want to bring in a host of off-the-shelf aero-improvement devices like skirts, which will go down along the wheels or various fairings which cover the gap between the tractor and the trailer," he continued. "[The goal is to] baseline those performances and see what kind of device has the most potential and how [far] off the numbers are for these devices that are [currently being] sold."

Hartley said the current test, the first of its kind at NFAC's 80-foot-by-120 foot wind tunnel since 1994, subjected the tractor trailer and drag-reduction components to drag, side load and yaw [forces].

NFAC is a unique facility primarily used for determining aerodynamic characteristics of large-scale and full-scale rotorcraft and powered-lift vertical/short take off and landing aircraft, as well as testing of wind turbines, parachutes, trucks, and other non-traditional types of testing.

In 2006, the Air Force signed a lease with NASA to reopen NFAC after the facility closed in 2003 due to budget pressures. Full operational capability occurred in early 2008.

The facility is composed of two large test sections and a common, six-fan drive system. The 40-by-80 foot wind tunnel circuit, which was built in 1944, is capable of providing test velocities up to 300 knots. The 80-by-120 foot test section is the world's largest wind tunnel and is capable of testing a full size Boeing 737 at velocities up to 100 knots. A system of moveable vanes can be positioned so that air either drawn through the 80-by-120 foot test section and exhausted into the atmosphere, or driven around the closed circuit through the 40-by-80 foot test section. A passive air exchange systems is utilized in the 40-by-80 foot circuit to keep air temperatures below 125 degrees Fahrenheit. A wide range of available model support systems combine with this unique facility to allow successful completion of aerodynamic and acoustic experiments that cannot be achieved anywhere else.