High Velocity Jet Noise Source Location and Reduction. Task 5. Investigation of 'In-Flight' Aeroacoustic Effects on Suppressed Exhausts.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1979
- Accession Number
- ADA094297
Entities
People
- E. J. Stringas
- J. F. Brausch
- N. Baumgardt
- R. Mani
- W. S. Clapper
Organizations
- General Electric