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A Wind Tunnel Rig to Study the External Fan Cowl Separation Experienced by Compact Nacelles in Windmilling Scenarios

Accepted version
Peer-reviewed

Type

Conference Object

Change log

Authors

Boscagli, Luca 
Swarthout, Avery 
Tejero Embuena, Fernando 
Babinsky, Holger 

Abstract

Ultra high-bypass ratio aircraft engines adopt slim fan cowl profiles which are sensitive to separation on their external surfaces under diversion windmilling conditions, when engine shutdown occurs during cruise. A two-dimensional wind tunnel rig is developed to investigate the separation mechanisms experienced by aero-engine nacelles in such scenarios to establish the detailed aerodynamics. The tunnel flow field with entry Mach number 0.65 broadly replicates the expected diversion windmilling flow behaviour for a full-scale nacelle, featuring a supersonic region which terminates in a normal shock wave on the external fan cowl surface. For the three conditions investigated, which relate to different engine mass-flow rates, the response of the boundary layer in this region progresses from remaining fully attached through to well-established separation. However, the rig Reynolds number based on nacelle lip thickness is about 1.2 million, roughly one-third of full scale, resulting in a transitional rather than turbulent shock-boundary-layer interaction. Nevertheless, simple simulations correctly predict the wind tunnel flow field, except for the precise boundary-layer response to normal shock waves, and so experimental data from the rig can be used to validate relevant computational methods.

Description

Keywords

4012 Fluid Mechanics and Thermal Engineering, 40 Engineering, 7 Affordable and Clean Energy

Journal Title

AIAA SCITECH 2023 Forum

Conference Name

AIAA SCITECH 2023 Forum

Journal ISSN

Volume Title

Publisher

American Institute of Aeronautics and Astronautics
Sponsorship
European Commission Horizon 2020 (H2020) Industrial Leadership (IL) (101007598)