Inlet flow distortions entering turbofan engines create considerable design challenges and affect the performance of the propulsion system. The associated flows are always complex, containing elements of altered pressure and swirl. As an approach to decouple inlet total pressure distortion and inlet swirl distortion, two experimental investigations were designed and conducted. A total pressure distortion screen and a StreamVane™ swirl distortion device were installed individually in the inlet duct of a research turbofan engine rig, resulting in non-uniform flow entering the fan rotor. The two distortion devices were designed to create inlet flow profiles derived from conceptual next-generation aircraft configurations; a boundary layer ingesting S-duct inlet for the total pressure distortion device and a blended wing body inlet for the swirl distortion device. Three-dimensional flow parameters were measured in the bypass annulus at the fan rotor exit plane. Comparison of the resulting fan responses revealed that both distortions persisted through the fan rotor and created off-design conditions entering the fan exit guide vanes. The results from the investigation indicated that it was impossible to completely decouple total pressure and swirl distortion, although good separation of components was achieved. The radial and tangential flow angles at the fan outlet were more significantly influenced by the inlet swirl distortion; whereas, the total and static pressure ratios of the fan were more significantly influenced by the inlet total pressure distortion. The important outcome from this analysis is a better understanding of the fan rotor response to individual distortion devices, providing novel information toward development of combined pressure/swirl distortion research.
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