Effect of Various Inlet Distortion Patterns on Distortion Transfer and Generation at the Near-Stall Operating Point

An increased understanding of how inlet flow distortion affects transonic fans enables improved fan design and performance prediction. Inlet distortion refers to non-uniformities in the incoming flow properties. Complex inlet ducts in high performance aircraft result in distorted flow at the fan inlet. In this paper, Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations were used to investigate how the Pt gradient between the clean and distorted sector in the inlet profile affects distortion transfer and generation through a transonic fan. Variants with an increasingly more gradual Pt gradient at the boundary of the distorted sector were applied at the fan inlet. Simulations were conducted at the near-stall operating point. Fourier-based distortion descriptors were used to quantify levels of distortion transfer and generation at various axial locations. It is shown that variations in rotor incidence occur as a result of the applied Pt distortion at the inlet. A less abrupt Pt gradient diminishes the local extrema in rotor incidence, which in turn reduces the amount of distortion transfer and generation through the rotor. The near-stall condition experiences a 23.4% and 21.2% average reduction in the amount of distortion transfer and generation, respectively, at any span