2012 Transportation Cleantech - Airplanes

Illustration of drag reducing aircraft fuselage

The USDOE Office of Energy Efficiency and Renewable Energy (EERE) estimates that US aircraft consumed 1,040 thousand barrels (43.7 million gallons) of petroleum per day in 2010. This represents slightly less than eight (8) percent of the daily total transportation petroleum consumption in the country that year, and is slightly less than 25% of the daily car usage of petroleum. Still, 44 million gallons is a considerable volume, and steps to improve the fuel economy of aircraft can play a part in allowing us to more efficiently use our fossil fuel resources.

There are multiple ways of improving aircraft fuel efficiency, ranging from engine design, to flight profiles and routing (along with changes in air traffic control), to reducing the drag of the aircraft.

“System and method for drag reduction”

David T. Birkenstock of Herndon, VA was awarded patent US 8,113,466 of this title on February 14, 2012. Interestingly, this was the last day patents issued from the US Patent and Trademark Office prior to its closing the Green Technology Pilot Program two days later. Birkenstock did not take advantage of that program, which might be unfortunate, as it probably would have reduced the time from his initial filing to patent issuance by a considerable length of time.

The patent provides a fuselage design that reduces drag and allows thrust output, fuel efficiency or both to be maximized.  The rear portion of a body or motor vehicle may be modified to increase thrust output, fuel efficiency or both by creating a stagnation area, a suction inlet and a convex cusp area formed on the rear portion of the motor vehicle. Increasing the concavity or camber or sharpness of the radius of the stagnation area results in a greater local pressure coefficient, yielding greater thrust output. The size and shape of the suction inlet and the convex cusp area will also have an effect on thrust output and fuel efficiency.
Claim 1 states:

A method for increasing efficiency of an object moving through a fluid, comprising the steps of:

• forming a convex cusp area at substantially a rear of the object;
• extending one of a suction inlet and a blowing outlet with a convex transition portion on an end of said convex cusp area;
• extending a stagnation area from an end of said blowing outlet, said stagnation area having a concave shape;
• and varying a pressure thrust on said object by varying a sharpness of the convex cusp area.

Although the USPTO considers this to be an aircraft invention, Birkenstock’s claim wording, and the patent specification and drawings, show that some embodiments can include road vehicle design.  The USPTO examiners did not consider the auto sedan design aspects worthy of inclusion as cross-reference classifications, nor did they include any land vehicle classifications in their prior art searches. We include two drawings from the patent, one for an aircraft, and one for an auto sedan, showing Birkenstock’s drag reducing design concept.

Illustration of drag reducing auto sedan