Investigation on the inflow distortion of a propulsive fuselage aircraft and its impact on the propulsion fan performance

Boundary layer ingesting (BLI) propulsion represents a promising concept that can achieve a great fuel burn reduction compared to conventional aircraft. This study numerically investigates the BLI inflow distortion and its impact on propulsion fan performance using commercial software CFX. First, Reynolds-averaged Navier-Stokes (RANS) simulations were performed to obtain the inflow distortion of a propulsive fuselage aircraft with various geometries and flight conditions. Then, full-annulus URANS simulations were carried out to assess the effect of various inflow distortions on the performance of NASA rotor 67. The results show that the fuselage sweep dominates the BLI inflow distortion, while the effects of the wing and vertical tail are local. As the angle of attack increases, the BLI inflow distortion is alleviated due to the freestream being ingested from the bottom of the propulsor. With the increase in the angle of sideslip, the redistributing and impinging flow significantly aggravates the total pressure and swirl distortion. With regard to the fan performance, various BLI inflow distortions share a similar static pressure distribution upstream of the rotor, as a result of the comparable total pressure distribution, so the cases without swirl distortion show a similar distribution of migration-induced swirl angle. At the peak efficiency condition, a minimum reduction in efficiency of approximately 4.5% and a total pressure ratio reduction of over 2.9% are observed for the investigated inflow distortions, in comparison with the Clean case. Moreover, the findings reveal that the effect of swirl distortion on fan performance is minor for the cruise case, but substantial for the two sideslip cases. These results offer useful insights into BLI propulsion.