Acoustic optimisation and prediction of sound propagation in turbofan engine ducts

The research presented in this thesis explores the prediction of noise propagation and<br/>radiation in turbofan engine intakes and bypass ducts, and the optimisation of noise attenuation<br/>by using acoustic liners. A commercial FE/IE code ACTRAN/TM is used<br/>within two shell programs; B-induct for bypass ducts and ANPRORAD for intake ducts.<br/><br/>An automated liner impedance capability has been demonstrated by exploiting an optimisation<br/>suite, SOFT.<br/>Automated liner impedance optimisations to maximise the liner insertion loss have<br/>been performed for a uniform bypass duct with a multimodal noise source, by using<br/>B-induct within SOFT. Results show that, multi-segment liners are effective at low frequencies<br/>when few acoustic duct modes are present and less so at high frequencies when<br/>many modes are present. Other results show that, at high frequencies, having different<br/>liner impedances on the inner and outer walls could be more effective than axially segment<br/>liners. An automated liner impedance optimisation has also been performed for a realistic<br/>bypass duct, and an A-weighting has been considered.<br/><br/>Far field noise levels predicted by using ANPRORAD analysis have been validated<br/>against measured data from rig and engine tests. The predicted results are in good agreement<br/>with the measured data when the noise source is calibrated using in-duct measured<br/>values. This demonstrates that ANPRORAD is a viable methodology for intake noise<br/>predictions in industry. ANPRORAD has also been applied to investigate the effect of<br/>the intake geometry on low-frequency acoustic reflections in the intake, and integrated<br/>within SOFT to perform automated liner impedance optimisations to minimise acoustic<br/>reflections to the fan.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2010

Author dc:creator

• Achunche, Iansteel Mukum

Advisors dc:contributor.advisor

• Astley, R.J.
• Kempton, A.J.