June 27, 2013
Saw-tooth pattern improves noise profile of the Lufthansa 747-8
The Lufthansa Group remains committed to reducing aircraft noise emissions in order to minimise its impact on residents in the vicinity of airports. The greatest improvements can be achieved through the use of modern aircraft. That is why the Group is continuing to invest in the latest technology. Take the new Boeing 747-8, which has been in service with Lufthansa since 2012. Its noise footprint – like that of the Airbus A380 – is about 30 per cent smaller than the footprint of comparable predecessor models.
The Boeing 747-8 is powered by newly developed GEnx-2B67 engines, which have a saw-tooth pattern on the trailing edges of the jet engine nozzles. These so-called chevron nozzles enhance the mixing rate of the turbulent shear layer, i.e. the layer of air between the hot, fast-moving exhaust gas stream from the interior of the engine and the cold secondary air that flows around the engine core. Chevron nozzles help to significantly reduce pressure fluctuations and thus jet noise. In the case of GEnx engines, the saw-tooth concept is also applied to the outer trailing edge in order to reduce the noise emissions generated there.
As long ago as 2001, Lufthansa and the German Aerospace Centre (DLR) conducted a series of tests to measure the flyover noise generated by an Airbus A319 fitted with a chevron nozzle. The measurements demonstrated that the nozzle reduced the jet noise by about 1 dB(A).