Aerodynamic Shape Optimization of the STARC-ABL Concept for Minimal Inlet Distortion

The NASA single-aisle turboelectric aircraft with an aft boundary layer propulsor (STARC-ABL) concept utilizes a novel electrically driven aft fan that ingests the fuselage boundary-layer for increased propulsive efficiency. In this paper we examine how aerodynamic shaping of the fuselage diffuser and nacelle inlet can reduce the flow distortion at the aft fan. Adjoint-based aerodynamic shape optimization with the ARP1420 distortion metric objective is used to automatically determine the optimal shapes for minimal fan-face distortion. Single and multipoint optimizations are carried out for simplified body-duct and wing-body-duct configurations. These two configurations highlight the importance of including the wing downwash effects when designing the propulsor. The optimizations showed the body-duct configuration can obtain cruise distortion values of approximately 1% while the wing-body-duct configuration can obtain distortion values of just over 2%.