Abstract
Boundary layer ingesting aircraft configurations create substantial flow distortions in inlets of turbofan engines and alter propulsive efficiency and performance. The swirl distortion component of these inlet flow profiles changes the incidence angle of air entering the fan which alters the amount of flow turning and work performed by the fan. This paper presents the results of an experimental investigation of fan response to inlet swirl distortions in an operating turbofan engine. Three-dimensional flow measurements were taken in the bypass annulus behind the fan rotor of a Pratt & Whitney Canada JT15D-1 turbofan research engine rig experiencing inlet distortion from a StreamVane swirl distortion generator. The StreamVane was designed to impose a swirl distortion profile matching a computational fluid dynamics model of a conceptual blended wing body aircraft engine inlet. Results from the investigation revealed that the swirl distortion altered the fan rotor flow turning, persisted downstream of the fan rotor plane, and entered the fan exit guide vanes. When compared to non-distorted inlet flow, the average fan outlet total-to-atmospheric pressure ratio decreased approximately 1.5%, while the flow angles exiting the fan deviated by up to ±10°. Both results indicate reductions in propulsor effectiveness and support the requirement for distortion tolerant fan optimization.
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