Aerodynamic Performance of an Aircraft with Aft-Fuselage Boundary Layer Ingestion Propulsion

Abstract

Boundary Layer Ingestion (BLI) is a technology that promises fuel consumption benefits for future civil aircraft. However, it introduces detrimental aerodynamic interactions between the propulsor and the airframe. In particular, the inflow to the BLI propulsor is affected by the flow around the airframe elements. The non-uniform inflow can influence the fan aerodynamic, aeroacoustic and aeroelastic performance. As a consequence, the fan design needs to tolerate the inlet distortions in all the flight phases. This paper discusses an experimental study of the aerodynamic performance of an aircraft with a BLI propulsor integrated at the aft-fuselage section, representative of a Propulsive Fuselage Concept (PFC) aircraft. Aerodynamic load measurements show that the BLI propulsor affects the longitudinal and lateral-directional equilibrium of the aircraft in off-cruise conditions. Flow measurements at the BLI propulsor inlet indicate that the fuselage boundary layer induces the strongest total pressure distortion. However, particularly at a non-zero sideslip angle, the vertical tail plane strongly affects the inflow to the BLI propulsor, introducing non-symmetric total pressure and velocity distortions. The analysis of the momentum and power fluxes in the flowfield show that around 20% of the total aircraft drag is produced in the fuselage boundary layer, while around 5% of the total aircraft drag power is dissipated in the fuselage wake. Furthermore, the BLI propulsor substantially reduces the axial kinetic energy flux in the fuselage boundary layer (the so-called "wake-filling" effect), suggesting an increased propulsive efficiency.

A Review of Novel and Non-Conventional Propulsion Integrations for Next-Generation Aircraft

“…The findings underscored the substantial impact of FPR on the required shaft power, revealing that a 10% reduction in FPR resulted in a remarkable 36% reduction in shaft power. On the other hand, a series of experimental studies confirmed preliminary simulations of this PFC aircraft [215][216][217]. Particle image velocimetry techniques were employed to investigate the main aerodynamic phenomena, and the power balance method was employed to evaluate the aerodynamic and propulsive forces.…”

Potential Propulsive and Aerodynamic Benefits of a New Aircraft Concept: A Low-Speed Experimental Study

“…In this paper, the use of the power balance method as the theoretical framework to determine the benefits of BLI ensured minimal impacts from Reynolds number variations, thereby allowing for the scaling of low-speed results to actual flight Reynolds numbers [16][17][18]. In recent years, experimental investigations have placed an emphasis on axi-symmetric PFC aircraft [19,20]. These studies focused on characterizing the flowfield surrounding the BLI propulsor and on evaluating the aerodynamic forces and moments under various flight conditions.…”