Ual747 From , joined Dec 1969, posts, RR: Posted (13 years 7 months 2 weeks 4 days 16 hours ago) and read 4697 times:
SEATTLE, Nov. 20, 2001 -- Boeing Commercial Airplanes and Rolls-Royce Aero Engines have completed a noise reduction flight test program that promises to make quiet jets even quieter.
Known as the Quiet Technology Demonstrator (QTD), a Rolls Royce Trent 800 engine was modified with a package of noise reduction technologies developed collaboratively by the two aerospace companies. Using a 777-200ER, the three week flight-test demonstrated noise levels significantly below those of a standard 777, which is known as one of the quietest airplanes in service today. Takeoff jet exhaust noise was reduced by up to four decibels and inlet fan noise was reduced by up to 13 decibels.
Engineers used saw-tooth-shaped aerodynamic devices at the rear of the nacelle and on the exhaust nozzle to control the mixing of the hot jet exhaust, the bypass stream and the ambient air. The shape of the devices was determined by computational fluid dynamics modeling and verified in wind tunnel tests using scale models.
Fan noise also was reduced with extensive acoustic improvements to the redesigned engine nacelle inlet. A new technology called Amax (area maximization) increased by 30 percent the area of acoustic treatment in the inlet casing. A new lining design was used that reduces objectionable "buzz saw" noise passengers often hear during takeoff and climb.
The flight tests, conducted at Boeing's Glasgow, Mont., airfield, verified the computer and laboratory results. Some 200 microphones were placed on the ground along the flight path, and 100 microphones were affixed to the 777. Teamed with computers, the microphones became an "acoustic camera" that accurately and dynamically pinpointed high-frequency noise sources on the airplane as it took off, flew the flight test pattern and landed again. This ground noise monitoring capability was made possible by NASA sponsorship.
Although the purpose of the QTD program was to reduce noise heard on the ground, levels within the cabin -- equally important to the airlines - also were analyzed. Nearly 100 microphones placed along the entire length of the cabin registered a reduction of forward cabin buzz-saw noise by seven decibels.
The culmination of years of work, these successful tests mark one of the final stages before QTD noise reduction technology is implemented in service. Combined with airframe noise reduction and engine redesign efforts being pursued separately, the new technologies can be incorporated on a new airplane program or as a retrofit to airplanes in service.
RayChuang From United States of America, joined Jun 2000, 8187 posts, RR: 4
Reply 8, posted (13 years 7 months 2 weeks 4 days 14 hours ago) and read 4444 times:
My guess is that this new engine nacelle breakthrough is just the thing to make new airplanes compliant with the toughest noise-emission standard for airplanes in the world--LHR's so-called QC2 standard.
Rolls-Royce might apply this to the nacelle of the Trent 900's that will be installed on the A380-800, that's to be sure.
AWspicious From , joined Dec 1969, posts, RR:
Reply 11, posted (13 years 7 months 2 weeks 4 days 12 hours ago) and read 4395 times:
Reminds me of a cookie cutter
I assume they used the 777 as a test platform because it represents the cutting edge of civil aviation technology. (pardon the pun) They took one their most advanced engines and tried to make it even better. Push the envelope, if you will.
Perhaps, they felt it was better to demonstrate their ability to improve on technology that was designed for tomorrow than on technology that's almost past it's time.
Hkg_clk From Hong Kong, joined Jan 2001, 999 posts, RR: 2
Reply 13, posted (13 years 7 months 2 weeks 4 days 9 hours ago) and read 4306 times:
That saw-tooth shape nacelle looks cool!! I guess they're testing it on the 777 as it has the longest production cycle remaining and will therefore have to comply with many new regulations in the future.
I thought some manufacturers were going to use noise cancellation technology at one point? Did it not work?
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