Active control of fan tones radiated from turbofan engines. I. External error sensors

Joseph, P., Nelson, P. A. and Fisher, M. J. (1999) Active control of fan tones radiated from turbofan engines. I. External error sensors. Journal of the Acoustical Society of America, 106 (2), 766-778. (doi:10.1121/1.427095).

Abstract

This paper is the first of two papers dealing with the active control of fan tones radiated from the intake of turbofan engines. The present paper describes an idealized mathematical model for the prediction of the sound transmission and radiation of harmonic sound from a finite-length, unflanged hollow hard-walled circular duct containing a subsonic axial mean flow. The paper proceeds to use this model in computer simulations aimed at assessing the potential for reducing the far-field radiated sound by active means using two rings of discrete secondary sources on the duct wall. Perfect knowledge of the sound field to be controlled is assumed throughout. The paper investigates two control objectives. The first is concerned with minimizing the total sound power transmitted along the duct, and hence the total sound power radiated. The other is concerned with minimizing the radiated sound power radiated into a specified band of sideline solid angles. Implicit in this investigation is the assumption of perfect observability of the radiated far field equivalent to a large number of error sensors located in the far field. The corresponding performance for the two control objectives when the observability of the sound field is limited to measurements made by a number of the error sensors situated on the duct wall is the subject of the companion paper.

This record has no associated files available for download.

Contributors

Author: P. A. Nelson

Download statistics