HIGH VELOCITY JET NOISE SOURCE LOCATION AND REDUCTION. TASK 5. INVESTIGATION OF 'IN-FLIGHT' AEROACOUSTIC EFFECTS ON SUPPRESSED EXHAUSTS

The flight noise characteristics in terms of peak noise, directivity and spectra were projected for five suppressor nozzle designs. Static and flight suppression levels were established using conical nozzle data as a reference. The noise characteristics were determined by testing each nozzle design in the anechoic free jet facility and then applying a transformation to account for dynamic effects. The transformation process is described and a computer program with instructions is presented. Each of the five suppressor nozzles was selected by balancing suppression level, performance loss, and mechanical complexity. Weight estimates and performance estimates are presented. An assessment is made on how these suppressors affect the noise versus performance trades for typical variable cycle engine (VCE) operating conditions. Suppressors are found to have minimal peak noise suppression loss in flight at high velocities. As mass average velocity decreases, the flight peak noise suppression levels are less than those measured statically from 0 to 5 PNdB. In all cases, the suppressors were quieter than the conical nozzle in flight. In the forward quadrant, multielement suppressors are effective in reducing shock noise; also, the forward quadrant noise for a suppressor is not amplified to the same degree as a conical nozzle. Overall suppression characteristics measured statically are different than in-flight and are function of the specific suppressor design. (Author)

• Supplemental Notes:
  • See also Task 6, Supplement, AD-A094 298.
• Corporate Authors:

  General Electric

  Marine Turbine & Gear Engineer, 1100 Western Ave
  Lynn, MA  United States  01910

  Federal Aviation Administration

  800 Independence Avenue, SW
  Washington, DC  United States  20591
• Authors:
  • Baumgardt, N
  • Brausch, J F
  • Clapper, W S
  • Mani, R
  • Stringas, E J
• Publication Date: 1979-1

Media Info

• Pagination: 194 p.

Subject/Index Terms

• TRT Terms: Acoustic measuring instruments; Acoustics; Aircraft exhaust gases; Aircraft noise; Anechoic chambers; Computer programs; Electromagnetic spectrum; Engines by cycle; Exhaust gases; Flight; Flow; Jet engines; Losses; Noise control; Nozzles; Peak periods; Performance; Static tests; Suppressors; Transformations (Mathematics); Values in measurement; Velocity; Weight
• Uncontrolled Terms: High velocity; Noise reduction; Sources
• Old TRIS Terms: Acoustic measurement; Conical nozzles; Exhaust nozzles; Inflight; Jet engine noise; Jet flow; Nozzle area ratio; Peak values; Performance engineering; Suppression; Variable cycle engines
• Subject Areas: Environment; Vehicles and Equipment;

Filing Info

• Accession Number: 00328897
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: R78AEG628, FAA-RD-76-79-5
• Contract Numbers: DOT-OS-30034
• Files: NTIS, USDOT
• Created Date: May 21 2003 12:00AM