A jury of Airbus and independent technology experts will choose a winner on 12 June in the airframer's 2013 Fly Your Ideas challenge, a biennial UNESCO-sponsored design competition dating to 2008 that is principally aimed at encouraging students to pursue careers in aerospace engineering. It has also fed some good ideas into the Airbus innovation pipeline.

Of the five finalists - from Malaysia, Australia, Italy, Brazil and India, whittled down from upwards of 600 proposals from 82 countries - competing for the €30,000 ($39,000) top prize, one that stands out as a near-term possibility is a concept for an airliner fuelled by a cryogenic blend of sustainably produced liquefied biomethane and liquefied natural gas (bio-LNG).

Depending on the biomethane-to-LNG blend ratio, the Royal Melbourne Institute of Technology team behind the Cryogenic Liquid Methane Aircraft (CLiMA) reckons its approach could result in a 20-97% net reduction in carbon dioxide emissions.

A major challenge in achieving this hybrid fuel propulsion system is efficient storage of relatively low-density bio-LNG, to either restrict or promote boil-off when required. One promising configuration includes the use of in-wing box tanks and underwing fuel tank pods.

CLiMA academic advisor Graham Dorrington says the team has concluded that mounting the engines and external fuel pods under the wings is probably good, on the principle that distributed wing load is attractive, but that design also allows for much shorter thermally insulated fuel lines.

"We were also driven by a self-imposed design requirement to minimise the possibility of any build up of a methane plus air mixture in any internal spaces," says Dorrington. "This precluded, or disadvantaged, the selection of any bio-LNG fuel systems inside the fuselage, although we did permit a sealed through-wingbox insulated tank and port-starboard fuel transfer."

Although the cost of ground infrastructure remains an unknown, Dorrington is enthusiastic about the concept: "The longer we have looked at the LCH4 aircraft option, the more convinced we have become that it can be done in the near term. The aircraft is the easy bit of jigsaw."

Source: Flight International