Acoustic liner optimisation and noise propagation through turbofan engine intake ducts

Abstract

The research in this thesis explores the prediction of fan noise propagation through turbofan engine intakes and its radiation to the far-field. The performance of acoustic liners installed in intakes to attenuate noise is the focus of the study. A commercial CAA (Computational AeroAcoustics) code ACTRAN/TM and an in-house shell code ANPRORAD developed at the ISVR are used to predict the performance of acoustic liners throughout the studies presented in this thesis. An automated system for running computations for a large number of cases with different liner impedance and engine operating conditions has been developed and applied for optimising liners for maximum noise benefit. The intake liner configuration of main interest is an intake lip liner. The performance of liners are investigated for broadband and tone noise source components of fan noise. In the study for an intake lip liner, an optimum single layer was identified based on the optimisations. A series of no-flow scale rig tests were conducted in the anechoic chamber at the ISVR and the test data have been appraised by comparing with numerical predictions. Reasonable agreements have been achieved, and the lip liner showed measurable noise benefit. Numerical predictions of a lip liner performance have also been performed for a fan rig intake tested in the presence of flow.

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