Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake

Hall, David G.; Heidelberg, Laurence J.; Konno, Kevin E.

doi:10.2514/6.1993-599

Cited by 14 publications

(11 citation statements)

References 3 publications

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“…4 The resolution of circumferential modes arise from a Doppler induced frequency shift due to the unique and discrete rotation rate of each m-order imparted by the continuous rotation of the rake. 5 Radial modes are computed from a least squares data fit of the radial pressure profile using the hardwall Bessel functions as the basis functions. 6 The modal data from the rotating rake are presented in 3-D format.…”

mentioning

confidence: 99%

Duct Mode Measurements on the TFE731-60 Full Scale Engine

Sutliff¹,

Konno²,

Heidelberg³

2002

8th AIAA/CEAS Aeroacoustics Conference &Amp;amp; Exhibit

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mentioning

confidence: 99%

Duct Mode Measurements on the TFE731-60 Full Scale Engine

Sutliff¹,

Konno²,

Heidelberg³

2002

8th AIAA/CEAS Aeroacoustics Conference &Amp;amp; Exhibit

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“…A more complete description of the data collection and analysis is presented in a companion paper. 5 …”

Section: Mndel Fanmentioning

confidence: 99%

“…A complete discription of the measurement technique and data analysis is presented in a companion paper. 5 The object of the present study is to measure the modal structure in the inlet of the ADP for three inlet lengths and two stator vane blade numbers. One stator was designed to have no cuton modes at the blade passing frequency (BPF) while the other was designed for a single circumferential order.…”

Section: Introductionmentioning

confidence: 99%

Heidelberg

Hall²

1993

31st Aerospace Sciences Meeting

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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-Ft Anechoic Wind Tunnel. Three inlet configurations were tested with cuton 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 cuton stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cutoff stator.

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“…The easiest way to measure the transfer function is to send a signal to the actuators and to measure the microphone outputs without the primary noise sources. The transfer function can be easily calculated as: VM C=Xcal/Ycal=(Xcal/Ycal)_MM =CMVM yn(9) where C M = Xcal/Yca1 is mth modal transfer function coefficient. Its inverse is given asC-1= Ycal/Xcal = (1/CM)V M vH = C_ VM V H (10)By multiplying both sides of Eq.…”

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confidence: 99%

Active noise control of low speed fan rotor-stator modes

Sutliff¹,

Pla

et al. 1997

3rd AIAA/CEAS Aeroacoustics Conference

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This report describes the Active Noise Cancellation System designed by General Electric and tested in the NASA Lewis Research Center's 48 inch Active Noise Control Fan. The goal of this study was to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for active noise cancellation of fan tones. The control system is based on a modal control approach. A known acoustic mode propagating in the fan duct is canceled using an array of flush-mounted compact sound sources. Controller inputs are signals from a shaft encoder and a microphone array which senses the residual acoustic mode in the duct. The canceling modal signal is generated by a modal controller.The key results are that the (6,0) mode was completely eliminated at 920 Hz and substantially reduced elsewhere. The total tone power was reduced 9.4 dB. Farfield 2BPF SPL reductions of 13 dB were obtained.The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB modal PWL decrease. Global attenuation of PWL was obtained using an actuator and sensor system totally contained within the duct.

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Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake - Data collection/analysis techniques

Cited by 14 publications

References 3 publications

Duct Mode Measurements on the TFE731-60 Full Scale Engine

Duct Mode Measurements on the TFE731-60 Full Scale Engine

Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake

Active noise control of low speed fan rotor-stator modes

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