Aft Fuselage Boundary Layer Ingesting Propulsion System Design

This paper describes the conceptual design of a turbo-electric, single-aisle, mid-range aircraft with tail-integrated distributed propulsors for boundary layer ingestion (BLI). Six tail-BLI propulsors, driven by 0.5 MW electric motors, are installed on the aircraft, with a non-axisymmetric aft fuselage and a T-tail, in addition to two underwing turbofan engines. The estimated fuel burn benefit is 8.5% in Payload Range Fuel Consumption at a cruise Mach number of 0.8, compared to the baseline. The non-axisymmetric aft fuselage creates swirl into the tail-BLI propulsors, with the fan rotational direction chosen for co-swirl to reduce incidence. The number and size of the tail propulsors are set by the fuel burn trade, between maximizing ingested boundary layer kinetic energy defect and minimizing propulsion system weight. The propulsor fan pressure ratio is set by the trade between propulsor weight and propulsive efficiency. The paper presents a rigorous assessment of the potential for fuel burn reduction with tail-integrated, BLI, distributed propulsors and gives guidelines concerning the design features that enable this improvement in fuel burn.