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PlayHunting down noise! Since May 2012, Lufthansa 747-8 uses engines of a design, to say the least, unusual... Thanks to the particular "sawtooth" form of their exhaust nozzles, these “GEnx's” can significantly reduce noise. How? This is the latest innovation from General Electric; "saw-tooth" engines. Over and above the aesthetics, this design, in particular, significantly reduces the noise emitted by the engines. Concerned about its environmental impact, the German national airline Lufthansa has decided to equip its 20 Boeing 747-8’s with these fashionable engines, which are 30% quieter than the 747-400. « The jet noise is produced because you have different streams of the engine : the hot stream and the by-pass stream… And both streams have different velocity, and you have the shear layer bewtween those two streams at the trailing edge of the engine and in this shear layer you have a lot of turbulences, and therefore pressure fluctuation. And so noise is generated. And this shear layer is modified in a way that the turbulences is decreased and therefore the sound is decreased ». A not insignificant decrease of several decibels, especially for people living near airports. For example, the limits set for a jumbo in approach phase is around 105 decibels. In fact, a 747-8 or A380 rarely exceeds 100. And even though today, planes and helicopters in service meet ALL the norms of the noise certification standards adopted by the International Civil Aviation Organization ( I.C.A.O. ), being below these limits, for certain carriers, is a priority. To demonstrate the success of the GEnx, more than 1,300 are on order. Several companies are already using them on their Dreamliner’s or 747-8’s.
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Hunting down noise! Since May 2012, Lufthansa 747-8 uses engines of a design, to say the least, unusual... Thanks to the particular "sawtooth" form of their exhaust nozzles, these “GEnx's” can significantly reduce noise. How? This is the latest innovation from General Electric; "saw-tooth" engines. Over and above the aesthetics, this design, in particular, significantly reduces the noise emitted by the engines. Concerned about its environmental impact, the German national airline Lufthansa has decided to equip its 20 Boeing 747-8’s with these fashionable engines, which are 30% quieter than the 747-400. « The jet noise is produced because you have different streams of the engine : the hot stream and the by-pass stream… And both streams have different velocity, and you have the shear layer bewtween those two streams at the trailing edge of the engine and in this shear layer you have a lot of turbulences, and therefore pressure fluctuation. And so noise is generated. And this shear layer is modified in a way that the turbulences is decreased and therefore the sound is decreased ». A not insignificant decrease of several decibels, especially for people living near airports. For example, the limits set for a jumbo in approach phase is around 105 decibels. In fact, a 747-8 or A380 rarely exceeds 100. And even though today, planes and helicopters in service meet ALL the norms of the noise certification standards adopted by the International Civil Aviation Organization ( I.C.A.O. ), being below these limits, for certain carriers, is a priority. To demonstrate the success of the GEnx, more than 1,300 are on order. Several companies are already using them on their Dreamliner’s or 747-8’s.
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Lufthansa hunting down noise !

21/02/2013

DESCRIPTION : Since May 2012, Lufthansa 747-8 uses engines of a design, to say the least, unusual... Thanks to the particular "Chevron nozzle" form of their exhaust outlets, these “GEnx's” can significantly reduce noise. How ?

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