An analytical model is developed for active noise control (ANC) of tonal inlet noise from turbofan engines. An aeroacoustic model of the fan is used to determine the complex amplitude of the spinning acoustic modes. The control inputs are modeled as monopole acoustic sources located on the periphery of the engine inlet duct. The error sensors can be either far field microphones of disturbed inlet pressure transducers mounted on the inlet wall. The optimum control inputs to the secondary sources are obtained by minimizing the sum of the error sensor mean-squared-values. These control inputs are then applied to the secondary sources to compute the controled acoustic field. The main goal in using this model is to analytically explore the basic mechanisms and potential of this ANC technique in attenuating tonal inlet noise. The results shows that for the case of far-field sensors the control mechanism is the duct modal re-structuring which yields a weak radiating source at the inlet opening. On the other hand, using inlet sensors the attenuation in radiated power is achiewed by suppression of the significant radiating modes.
An analytical study of active control of narrow-band turbofan inlet noise
Analytische Studie aktiver Minderung des Schmalband-Einlaufgeräusches eines Mantelstromtriebwerks
1995
8 Seiten, 10 Bilder, 4 Tabellen, 13 Quellen
Conference paper
English
An Analytical Study of Active Control of Narrow-Band Turbofan Inlet Noise
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