| タイトル | Reduction of blade-vortex interaction noise through higher harmonic pitch control |
| 著者（英） | Wilbur, Matthew L.; Jolly, J. Ralph, Jr.; Brooks, Thomas F.; Booth, Earl R., Jr.; Yeager, William T., Jr. |
| 著者所属（英） | NASA Langley Research Center|Planning Research Corp.|Army Aviation Systems Command |
| 発行日 | 1990-01-01 |
| 言語 | eng |
| 内容記述 | An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels. |
| NASA分類 | ACOUSTICS |
| レポートNO | 90A23937 |
| 権利 | Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/358170 |
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