Active Control of Low Frequency Buzz-Saw Tones;Theory and Experiment

Abstract

This paper discusses some theoretical and experimental issues related to the active control of buzz-saw tones radiated from an aircraft engine inlet at takeoff. Buzz-saw tones occur when the rotor tip speed becomes supersonic. It arises due to the formation of shocks at the blade tips, which then propagate non-linearly along the engine duct. Buzz-saw noise comprises a series of tones harmonically related to the shaft rotation frequency (Engine Orders). Moreover, it has been shown that the noise at each Engine Order comprises just one single spinning mode. Whilst there has been considerable work aimed at assessing the feasibility of active control for reducing the tones due to rotor – stator interaction, buzz-saw noise has been overlooked. This is surprising given the low frequencies at which Buzz-Saw noise occurs, and its simple modal content, which both suggest that buzz-saw noise is particularly suited to active control. This paper describes various control strategies for reducing buzz-saw noise. The paper concludes with the results of a laboratory experiment aimed at demonstrated experimentally the effectiveness with which a single spinning mode, characteristic of an EO = 3 buzz-saw tone, can be controlled. Reductions in excess of 14dB are reported at some frequencies.

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References

Joseph

P.F.

Fruteau

, and Nelson

P. A.

. Design rules and sensing strategies for the active control of turbofan engine noise. In 7th AIAA/CEAS Aeroacoustics Conference, Maastricht, 2001.

Berge

Bouty

, and Cailleau

J.M.

. Active noise control of a jet engine at low frequency radiation: B.E.M. for predicting far-field noise reduction. 15th AIAA Aeroacoustics Conference, Long Beach, 1993.

Kraft

R.E.

and Kontos

K.B.

. Theoretical implications of active noise control for turbofan engines. In AIAA , editor, 15th AIAA Aeroacoustics Conference, Long Beach, 1993.

Burdisso

R. A.

Fuller

C. R.

, and Smith

J.P.

. Experiments on the active control of a turbofan inlet noise using compact, lightweight inlet control and error transducers. In AIAA/CEAS Aeroacoustics Conference, Munich, 1995.

Gerhold

Carl H.

. Active control of fan-generated tone noise. AIAA Journal, 35(1):17–22, 1997. NASA Langley Research Cent, Hampton, VA, USA.

Vaidya

P.G.

. Multiple pure tone generation in aeroengine fans at subsonic and supersonic relative tip speeds. AIAA Journal, 22(10):1366–1374, 1984.

Morfey

C. L.

and Fisher

M. J.

. Shock-wave radiation from supersonic ducted rotor. Aeron J, 74(715):579–85, 1970.

McAlpine

and Fisher

M. J.

. On the prediction of ‘buzz-saw’ noise in aeroengine inlet ducts. Journal of Sound and Vibration, 248(1):123–149, 2001.

Wilkinson

M. J.

. Active Control of Low Frequency Buzz-Saw Tones. PhD Thesis, University of Southampton 2004.

10.

Comparison of strategies for the active control of buzz-saw tones. 2006. AIAA journal, Vol 44(6), 1150–1157.

11.

Elliott

S.J.

Stothers

I.M.

, and Nelson

P.A.

. A multiple error lms algorithm and its application to the active control of sound and vibration. IEEE transactions on acoustics, speech and signal processing, ASSP-35(10):1423–1434, 1987.