Aft Fuselage Boundary Layer Ingesting Propulsion System Design

Abstract This article 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 nonaxisymmetric 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 nonaxisymmetric 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 boundary layer kinetic energy defect ingestion and minimizing propulsion system weight. The propulsor fan pressure ratio is set by the trade between propulsor weight and propulsive efficiency. The article 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. The distributed aft fuselage BLI propulsion system is suggested to offer a relevant pathway for tube-and-wing configurations with a potential major advancement in fuel burn reduction.