Accession Number:

ADA094297

Title:

High Velocity Jet Noise Source Location and Reduction. Task 5. Investigation of 'In-Flight' Aeroacoustic Effects on Suppressed Exhausts.

Descriptive Note:

Final rept. Dec 76-Jul 78,

Corporate Author:

GENERAL ELECTRIC CO CINCINNATI OH AIRCRAFT ENGINE GROUP

Report Date:

1979-01-01

Pagination or Media Count:

194.0

Abstract:

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

Subject Categories:

  • Test Facilities, Equipment and Methods
  • Acoustics
  • Fluid Mechanics
  • Fuels

Distribution Statement:

APPROVED FOR PUBLIC RELEASE