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  • AIRCRAFT PROPULSION AND POWER  (2)
  • Acoustics  (2)
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  • 1
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    Effects of vane/blade ratio and spacing on fan noise (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The effects of vane/blade ratio and spacing on fan noise are investigated to develop a fan noise prediction scheme which is calibrated against experimental data. A 44 blade, 0.504 diameter fan is used to demonstrate the production of fan noise data free from excess noise caused by rotor turbulence interaction. Two stator sets consisting of a cut-off set with 86 vanes, and a cut-on set of 48 vanes are used, with a total range of spacing from 0.5 to 2.3 rotor chords. The model includes viscous wake interaction noise and the potential field interactions of both the rotor and stator. A free-field acoustic environment is achieved by covering the walls, ceiling and floor with 0.7 m polyurethane foam wedges, providing less than + or - 1 dB standing wave ratio at 200 Hz. Only a 3 dB drop in tone level occurs as the spacing is increased from 0.5 to 2.3 rotor chords, and results indicate that the rotor wakes impinging on the stator vanes are the principal noise source for subsonic rotor speeds.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 81-2033 , Aeroacoustics Conference; Oct 05, 1981 - Oct 07, 1981; Palo Alto, CA
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
  • 2
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    AST Critical Propulsion and Noise Reduction Technologies for Future Commercial Subsonic Engines: Separate-Flow Exhaust System Noise Reduction Concept Evaluation (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This report describes the work performed by General Electric Aircraft Engines (GEAE) and Allison Engine Company (AEC) on NASA Contract NAS3-27720 AoI 14.3. The objective of this contract was to generate quality jet noise acoustic data for separate-flow nozzle models and to design and verify new jet-noise-reduction concepts over a range of simulated engine cycles and flight conditions. Five baseline axisymmetric separate-flow nozzle models having bypass ratios of five and eight with internal and external plugs and 11 different mixing-enhancer model nozzles (including chevrons, vortex-generator doublets, and a tongue mixer) were designed and tested in model scale. Using available core and fan nozzle hardware in various combinations, 28 GEAE/AEC separate-flow nozzle/mixing-enhancer configurations were acoustically evaluated in the NASA Glenn Research Center Aeroacoustic and Propulsion Laboratory. This report describes model nozzle features, facility and data acquisition/reduction procedures, the test matrix, and measured acoustic data analyses. A number of tested core and fan mixing enhancer devices and combinations of devices gave significant jet noise reduction relative to separate-flow baseline nozzles. Inward-flip and alternating-flip core chevrons combined with a straight-chevron fan nozzle exceeded the NASA stretch goal of 3 EPNdB jet noise reduction at typical sideline certification conditions.
    Keywords: Acoustics
    Type: NASA/CR-2000-210039 , E-12237 , NAS 1.26:210039 , R98AEB152
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Critical Propulsion and Noise reduction Technologies for Future Commercial Subsonic Engines. Area of Interest 14.3: Separate Flow Exhaust System Noise (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This presentation discusses: Project Objectives, Approach and Goal; Baseline Nozzles and Test Cycle Definition; Repeatability and Baseline Nozzle Results; Noise Reduction Concepts; Noise Reduction Tests Configurations of BPR=5 Internal Plug Nozzle adn Acoustic Results; Noise Reduction Test Configurations of BPR=5 External Plug Nozzle and Acoustic Results; and Noise Reduction Tests Configurations of BPR=8 External Plug Nozzle and Acoustic Results.
    Keywords: Acoustics
    Type: Separate Flow Nozzle Test Status Meeting; 181-254; NASA/CP-2000-210524
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    The effect of throttling on forward radiated fan noise (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A study was undertaken to evaluate the effect of operating line throttling on inlet-arc noise from high speed fans. Experimental measurements on a 1/4-scale fan stage tested in an anechoic chamber, with and without inlet turbulence control devices, were utilized to assess the effect of constant speed throttling on the forward arc radiated noise characteristics. Different effects were observed in different speed ranges with different types of inflow turbulence control. These effects were correlated with some of the current theories on fan noise generation mechanisms, and partial success was achieved in attempting to relate the various theoretical models to the observed trends. The results of this study have an important bearing on estimating the noise characteristics of new fan designs from scaling the measured characteristics of previously tested fans.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 79-0640 , American Institute of Aeronautics and Astronautics, Aeroacoustics Conference; Mar 12, 1979 - Mar 14, 1979; Seattle, WA
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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