Aeroacoustic assessment of the performance of Over-Tip liners in reducing noise of an aerofoil over a flat surface

Palleja Cabre, Sergi, Tester, Brian and Bampanis, Georgois (2020) Aeroacoustic assessment of the performance of Over-Tip liners in reducing noise of an aerofoil over a flat surface. In AIAA AVIATION 2020 FORUM. American Institute of Aeronautics and Astronautics.. (doi:10.2514/6.2020-2608).

Abstract

The reduction of fan broadband noise in the next generation of Ultra-High By-pass-Ratio (UHBR) engines remains a key technology challenge for the foreseeable future. The Over-The-Rotor (OTR) liner concept has been studied as a technology with the potential to further reduce fan noise and significant noise reductions have been measured. This paper describes a fundamental experimental evaluation that represents the Over-Tip-Rotor liner as a static airfoil with its tip located over a flat plate containing a flush-mounted lined insert and separated from the airfoil tip by a small gap. Differences in measured far-field sound spectra and in source power estimates derived from post-processed spiral array data have shown broadband gap noise reductions of 5-10 dB, even in the absence of a tip gap. Over-tip liners are found to suppress noise sources when located in the immediate vicinity, irrespective of the generation mechanism, mainly due to back-reaction effects on the source. An analytical prediction model for the over-tip liner noise reduction, based on a point source located over an infinite lined plane, is evaluated and compared with the experimental data. The model captures the back-reaction effects and gives good agreement with the measured data, including the variation of noise reduction with increasing gap size.

This record has no associated files available for download.

Contributors

Author: Sergi Palleja Cabre

Download statistics