Blended Wing Hydrogen Tank Design Patent

Image from a Boeing patent for a hydrogen fueled blended wing body ring tank. The tank is the dark ring running around most of the fuselage. (Boeing/U.S. Patent and Trademark Office)

Boeing Tuesday received a patent for a tank that could store liquid hydrogen fuel with reduced weight on a blended wing-body aircraft.

The patent application, filed in 2006, shows an aircraft very much like one that Boeing is studying under a NASA contract (see image below).

Boeing has been looking at blended wing-body designs for decades because they promise much greater efficiency. Critics, however, argue that passengers would never go for an aircraft with no or few windows.

The new patent focuses on how to put hydrogen fuel tanks on a blended wing-body jet.

"It has been proposed that aircraft will eventually transition to hydrogen fuel for increased efficiency and to reduce emissions," according to the application. "Hydrogen as fuel is more efficient, offering higher energy content per mass. Accordingly, hydrogen promises increased payload and range for aircraft. In addition, hydrogen offers benefits in terms of emissions because it can be produced by electrolysis of water and produces water when it is burned."

But liquid hydrogen in high-pressure tanks requires approximately four times the volume as kerosene (which currently fuels jets), and prior designs using hydrogen have run into such challenges as not holding enough fuel, having inefficient aerodynamic shapes, adding too much weight and taking up too much space, Boeing wrote.

The patent's solution is a ring-shaped tank running around most of the fuselage.

"The ring tank may be continuous with no tank end domes typically found on cylindrical pressure tanks, reducing tank weight for a given fuel volume," Boeing wrote. "The ring tank configuration avoids increasing the aerodynamic shape of the aircraft and does not encroach on usable passenger or payload areas of the aircraft."

Artist's concept of an aircraft that could enter service in 2025 from a team led by Boeing.