Lufthansa has described the benefits of the chevron nozzles used in the GEnx-2B67 jet engines which power the 747-8, as part of its continuing attempts to reduce noise levels. The company said the nozzles enhance the mixing rate of the turbulent shear layer – 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. They also “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. The 747-8 has been in service with Lufthansa since 2012.