Claire - Clean Air Engine

MTU Aero Engines, in partnership with Bauhaus Luftfahrt, has launched an ambitious program designed to reduce the carbon dioxide emissions of aircraft engines. Its Clean Air Engine (Claire) technology project is to lower carbon dioxide emissions by up to 30 percent by 2035. By 2025, a reduction of up to 20 percent may well have been achieved. All of the key components for Claire are already available, have been successfully tested and meet MTU's expectations in terms of energy efficiency and cost-effectiveness.

Geared turbofan, the sure key to success
MTU's three-stage program bases on the geared turbofan: Using geared turbofan technology, which by then will have reached production maturity, plans are to lower carbon dioxide emissions by about 15 percent in the first stage. Key components of this propulsion concept are a high-speed low-pressure turbine, which is made by MTU, a high-pressure compressor built in partnership between MTU and Pratt & Whitney, and a gearbox specifically developed for the purpose by Italy's gearbox specialist Avio.

In a second step, carbon dioxide emissions will be further lowered, by approximately 20 percent, by 2025, through the use of a novel counter-rotating fan MTU had already developed and tested in the eighties. By 2035, finally, MTU expects the targeted reduction of up to 30 percent to have been achieved. The road to success here is equipping the counter-rotating geared turbofan with a recuperator.

Less noise
Claire will not only reduce carbon dioxide emissions compared with a conventional engine, but also its noise. Optimizing the geared turbofan will cut the perceived noise level in half. That will pay handsome dividends inasmuch as even today, noise control plays a significant part in the fleet planning of airlines. Quieter aircraft will permit the air traffic infrastructure to be used more efficiently by far.

Novel aircraft concepts
MTU expects further improvements in aviation's environmental performance to come from new aircraft concepts. This is a topic the Bauhaus Luftfahrt e.V. association, founded by MTU Aero Engines, Liebherr Aerospace, EADS and the Bavarian Ministry of Economic Affairs is pursuing. One of the key problems is how best to improve the integration of engines into aircraft platforms and so optimize aerodynamics. Overall, the Bauhaus Luftfahrt's concepts target a future air transportation system that makes air traffic on short- and medium-haul routes very, very quiet and provides maximum economy of resources and space.

Multi-fuel engines
Today's engines - with some minor modifications - could also be operated on biological fuel. Since aircraft powerplants are multi-fuel engines, they can burn fuel from biological material just as well as fossil kerosene. Examples are already flying: in South Africa, aircraft have for years been traveling on synthetic fuels.