The research presented in this thesis explores the prediction of noise propagation and radiation in turbofan engine intakes and bypass ducts, and the optimisation of noise attenuation by using acoustic liners. A commercial FE/IE code ACTRAN/TM is used within two shell programs; B-induct for bypass ducts and ANPRORAD for intake ducts. An automated liner impedance capability has been demonstrated by exploiting an optimisation suite, SOFT. Automated liner impedance optimisations to maximise the liner insertion loss have been performed for a uniform bypass duct with a multimodal noise source, by using B-induct within SOFT. Results show that, multi-segment liners are effective at low frequencies when few acoustic duct modes are present and less so at high frequencies when many modes are present. Other results show that, at high frequencies, having different liner impedances on the inner and outer walls could be more effective than axially segment liners. An automated liner impedance optimisation has also been performed for a realistic bypass duct, and an A-weighting has been considered. Far field noise levels predicted by using ANPRORAD analysis have been validated against measured data from rig and engine tests. The predicted results are in good agreement with the measured data when the noise source is calibrated using in-duct measured values. This demonstrates that ANPRORAD is a viable methodology for intake noise predictions in industry. ANPRORAD has also been applied to investigate the effect of the intake geometry on low-frequency acoustic reflections in the intake, and integrated within SOFT to perform automated liner impedance optimisations to minimise acoustic reflections to the fan.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:523206 |
| Date | January 2010 |
| Creators | Achunche, Iansteel Mukum |
| Contributors | Astley, Richard ; Kempton, A. J. |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/162395/ |
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