Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake
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In this paper, the inlet of the Advanced Ducted Propeller (ADP) in the NASA Lewis 9- by 15-foot Anechoic Wind Tunnel was measured using a continuously rotating microphone system.Abstract:
Comprehensive measurements of the spinning acoustic mode structure in the inlet of the Advanced Ducted Propeller (ADP) have been completed. These measurements were taken using a unique and previously untried method which was first proposed by T.G. Sofrin. A continuously rotating microphone system was employed. The ADP model was designed and built by Pratt & Whitney and tested in the NASA Lewis 9- by 15-foot Anechoic Wind Tunnel. Three inlet configurations were tested with cut-on and cutoff stator vane sets. The cutoff stator was designed to suppress all modes at the blade passing frequency. Rotating rake measurements indicate that several extraneous circumferential modes were active. The mode orders suggest that their source was an interaction between the rotor and small interruptions in the casing tip treatment. The cut-on stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cutoff stator.read more
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Fan Noise Source Diagnostic Test: Tone Modal Structure Results
TL;DR: In this paper, the results of both inlet and exhaust tone mode measurements are presented in terms of mode power for both circumferential and radial mode orders, and the results show benefits of vane sweep to be large, up to 13 dB in total tone power.
Proceedings ArticleDOI
A unique ducted fan test bed for active noise control and aeroacoustics research
TL;DR: The Active Noise Control Fan (ANCF) test bed as mentioned in this paper is a large diameter, low speed, axial fan test bed with an externally supported duct, which can be used both to investigate active noise control and for more general fan aeroacoustics research.
Journal ArticleDOI
Inlet acoustic mode measurements using a continuously rotating rake
TL;DR: In this article, the authors used a continuously rotating microphone system to measure the acoustic mode structure in the inlet of an advanced ducted propeller and tested three inlet configurations with cut-on as well as cut-off stator vane sets.
Inlet acoustic mode measurements using a continuously rotating rake
TL;DR: In this article, the authors used a continuously rotating microphone system to measure the acoustic mode structure in the inlet of an advanced ducted propeller and tested three inlet configurations with cut-on as well as cut-off stator vane sets.
Proceedings ArticleDOI
Baseline acoustic levels of the NASA Active Noise Control Fan rig
TL;DR: In this article, a continuously rotating microphone rake system with a least-squares data reduction technique was employed to measure these modes in the inlet and exhaust, and the Eversman finite element radiation code was run with the measured in-duct modes as input and the computed farfield results were compared to the experimentally measured directivity pattern.