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research-article

Coupled Fan-Stator Aerodynamic and Acoustic Response to Inflow Distortion

[+] Author and Article Information
Hafiz M. Atassi

113 Hessert Center Notre Dame, IN 46556 atassi@nd.edu

Alexey V. Kozlov

117 Hessert Center Notre Dame, IN 46556 akozlov@nd.edu

Amr A. Ali

400 Main Street Engineering & Technology Center - M/S 173-08 East Hartford, CT 06118 amr.ali@pw.utc.com

David A. Topol

400 Main Street, M/S 173-08 East Hartford, CT 06118 david.topol@pw.utc.com

1Corresponding author.

Manuscript received October 30, 2018; final manuscript received May 29, 2019; published online xx xx, xxxx. Assoc. Editor: Li He.

ASME doi:10.1115/1.4043963 History: Received October 30, 2018; Accepted May 30, 2019

Abstract

Turbofan rotor-stator aeromechanic and aeroacoustics modeling has been traditionally developed by considering separately the aerodynamic and acoustic response of the fan and the stator to inflow nonuniformities. The paper develops a model for the coupled fan-stator response for a realistic 3D geometry. The coupling mechanism is mainly carried by scattered waves bouncing back and forth between the fan and the stator. The relationship between sources and state elements at three regions (inlet (1), in-between fan and stator (2), and exit (3)) is derived in terms of a scattering matrix S. The model is applied to two fan configurations: (1) a fully subsonic fan, and (2) a transonic tip speed fan. The scattering matrix terms, up to the 5th blade passing frequency (BPF), are calculated using CAAT, an Euler based code. Results show coupling adds about 5 dB to the sound power level of the transonic fan configuration but has a small effect for the subsonic fan configuration. Analysis shows that, for the transonic configuration, the inlet mode at 1BPF propagates in regions 2 and 3 but is cut-off in region 1. This reinforces coupling by trapping the acoustic mode 1BPF in region 2. Although this trapped energy is mainly due to the fan wake 1BPF, the fan scatters this energy into higher order acoustic modes and thus produces a redistribution toward higher frequency of the acoustic spectra . Finally, adding a liner in region 2 mitigates the increase of energy due to coupling.

Copyright © 2019 by ASME
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