Design and Performance of a Boundary Layer Ingesting Fan

Abstract A Boundary Layer Ingesting fan is designed to function in a tail cone thruster configuration on an existing aircraft. This means that the fan ingests part of the boundary layer developing over the fuselage all around the circumference. While the fuselage drag induced on the ingested flow makes it possible to obtain a higher propulsive efficiency, it also means that the fan will operate in a severely distorted flow. In the configuration studied here the incoming flow will generally have a lower impulse near the hub, but also substantial non-axisymmetric components. The incoming flow profile is evaluated from a CFD model of a complete Fokker 100 aircraft modified with a tail cone thruster installed. Having the aircraft modeled in detail allows the extraction of the flow entering the fan inlet, which makes up the inlet boundary condition to design for. In order to make a rational design of the fan, the incoming flow is circumferentially averaged at each radial location to form the radial profile used in the design. A fan map is created to evaluate critical points in the operating envelope in order to demonstrate that the given design is stable in operation. Operation of the fan in static ground conditions is within the operating envelope of the fan without variable nozzle area.