Open rotor - an innovative aircraft engine concept can offer up to 15 per cent improved fuel efficiency

New engine concepts could reduce aircraft fuel consumption

Innovative aircraft engine designs could reduce fuel consumption by up to 15 per cent, a Chalmers University of Technology doctoral researcher has found.

Evaluating the geared turbofan and open rotor concept in her doctoral thesis, Linda Larsson has found the new designs could help considerably reduce the impact of the aviation industry on the environment.

"The two concepts have a propulsive efficiency; in other words, the energy generated by the core engine can be efficiently converted into thrust," Larsson said.

Unlike a regular turbofan, the geared turbofan features a large fan at the front of the engine, allowing it to operate at a lower speed than the turbine that drives it. A gearbox between the turbine and fan reduces the number of revolutions, allowing for a lighter turbine and higher turbine efficiency.

An open rotor engine generates most of the thrust from two counter-rotating propellers instead of a ducted fan. This enables a larger engine diameter and thus a higher propulsive efficiency, without resulting in excessively large and heavy engine nacelle.

"Both of the concepts demonstrated very good potential in terms of reducing fuel consumption: geared turbofan by up to 4 per cent and open rotor by up to 15 per cent. Naturally, though, the technology has to be developed and implemented," Larsson said.

The open rotor concept was studied in the 1980s after the oil crisis and resulting fuel price hikes, and it was apparent already then that it worked. However, fuel prices dropped and the technology lost its appeal. It is now starting to get noticed again.

"The cost of fuel is one of the biggest costs faced by airlines, and there are also obvious environmental reasons and political incentives to reduce fuel consumption and emissions. A great deal of research is being conducted on the open rotor concept right now, and I believe the concept could be in place around 2030," Larsson said.

The average annual increase in passenger kilometres travelled by air has been 5.8 per cent over the last 40 years, and fuel sales have increased by 2.2 per cent annually during the same period. New technological solutions are needed if aviation is to reduce its impact on the climate.

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