Fan Response to Boundary-Layer Ingesting Inlet Distortions

Abstract

The modeling capabilities of TURBO, an existing turbomachinery analysis code, have been extended to include the ability to solve the external and internal flow fields of a boundary-layer ingesting inlet. Flow solutions are presented and compared with experimental data for several high-Reynolds-number flows to validate the solver modifications. The upstream flowfield was coupled to a hypothetical compressor fan to present a fully developed distortion to the fan. Although the total pressure distortion upstream of the fan was symmetrical for this geometry, the pressure rise generated by the fan blades was not, because of the velocity nonuniformity of the distortion. Total pressure profiles at various axial locations are computed to identify the overall distortion pattern, how the distortion evolves through the blade passages and mixes out downstream of the blades, and where any critical performance concerns might be. Stall cells are identified that are stationary in the absolute frame and are fixed to the inlet distortion. Flow paths around the blades are examined to study the stall mechanism. Rather than a typical airfoil stall, it is observed that the nonuniform pressure loading in the radial direction promotes a three-dimensional dynamic stall. The stall occurs at a point of rapid incidence angle oscillation observed when a blade passes through a distortion and re-attaches when the blade sees more uniform flow outside the distortion.