University of Twente Student Theses


Numerical predictions of acoustic performance of folded cavity liners for turbofan engine intakes

Knepper, K.M. (2013) Numerical predictions of acoustic performance of folded cavity liners for turbofan engine intakes.

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Abstract:This report deals with the acoustic behaviour of folded cavity liners. It explains the need for effective liners in order to attenuate fan noise, after which it provides the reader with a quick overview of the fundamentals of acoustics required for understanding the concepts of liner theory. The SDOF and the DDOF liners, typically used in turbofan engine ducts, are described briefly, followed by the introduction of the advantage of folded cavity liners. For the numerical modelling of the folded cavity liner the finite element program COMSOL is used. The COMSOL model created for a folded cavity liner is validated against measured data and predictions obtained by using another finite element code, Actran TM. Parametric studies have been performed to investigate the influence of the geometric features of the liner such as the length, height and width on the liner performance. Also the effects of changing the resistance of the facing sheet and the septum as well the benefit of placing an additional septum have been investigated. Finally a simple method to approximately predict the performance of a combination of a folded cavity liner and a liner with different impedance arranged in series is proposed. It was confirmed to give good estimate of the equivalent acoustic impedance achieved by the series of the liners without requiring running a COMSOL analysis.
Item Type:Internship Report (Master)
University of Southampton, United Kingdom
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:acoustics, cavity liners, COMSOL
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