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Pin Head
14th Feb 2016, 03:57
Hi

Can I ask please what the purpose of the....

Acoustic panels and nozzle fences

Serve?

Both for noise cancelling?

Thank you

B737900er
14th Feb 2016, 11:04
Yes, the acoustic panel has thousands of tiny holes punctured into it. This allows bypass air to pass through which will reduce the noise.

lomapaseo
14th Feb 2016, 15:05
not so sure about air passing through it but it sure does screw up a sound reflecting surface

RVF750
14th Feb 2016, 16:36
The perforated inner skins on the nacelle front are very efficient at killing the reflected buzz from the fan. They make a huge difference to the noise footprint.

By Nozzle fence I'm not sure what you mean. At the back, the nacelle of a CFM Boeing 737 has a spine under and over the engine. The nacelle is constructed of a front section, bolted to the engine fan housing and the outer and inner doors hung from the top mounts and latched at the bottom. The Thrust reverser cowls are the rear section, which slide back and forward and run in tracks top and botttom. The lower faired lip at the rear is the cover for these door track mechanism. At the top is also the heat shield for the pylon.

You have a single large aerofoil on the side to creat a vortex over the leading edge at high angles of attack, and a smaller blade in the upper inside to deflect a small sprung hinged section of the outer Kreuger leading edge flap when thrust reversers are deployed.

Regards,

RVF

Turbine D
14th Feb 2016, 17:57
Supporting what RVF750 said, The perforations help to reduce the jet engine's fan noise by damping the energy response from the fan while directing the sound into a sound absorbing material, generally in the form of a honeycomb structure.

Golden Rivet
15th Feb 2016, 16:50
the strakes on the exhaust nozzle are there to straighten the airflow in an attempt to reduce the burning on the inboard face of the pylon.

Early 737NG aircraft suffered from pylon burning, and had a heat proof paint applied, which wasn't really up to the job.

Its still not brilliant, but its better than it was...