Aerodynamic Interaction of a Boundary-Layer-Ingesting Propeller with a Fuselage Aft-Cone

Abstract

For the next generation of transport aircraft, boundary-layer ingestion (BLI) is being proposed as a promising technology to reduce energy consumption. However, the aerodynamic interaction between the propulsor and the fuselage boundary layer has received little attention. In this study, an experimental approach is used to study the effect of a fuselage aft-cone-mounted propeller on the flow around a fuselage aftbody. An idealized fuselage model with an integrated rear propeller is tested in a low-subsonic wind tunnel. The loads on the propeller were measured directly with the use of a rotating shaft balance. Integration of the aft-fuselage pressure field allowed for a complete force decomposition. Operation of the propeller was shown to significantly increase pressure and friction drag on the fuselage. Furthermore, hot-wire measurements show that the turbulence characteristics of the fuselage boundary layer upstream of the propeller were altered by the propeller. Compared to the propeller-off measurement, a clear deviation from the universal log law was observed. Phase-locked hot-wire and embedded microphone data reveal small in-phase fluctuations with the propeller blade passage. Despite their persistence throughout the boundary layer, the fluctuations are not believed to significantly impact the mean inflow to the propeller or affect its performance. Despite their insignificant impact on propeller performance, the fluctuations could still be relevant in terms of noise and vibrations.