Flow Field and Power Balance of a Distributed Aft-fuselage Boundary Layer Ingesting Aircraft

Abstract

Boundary layer ingestion is a technology that can potentially deliver step improvements in fuel burn. This paper presents a first investigation into the flow field and the performance breakdown of a distributed aft-fuselage boundary layer ingesting tube-and-wing aircraft using fully coupled Unsteady RANS calculations that resolve the complete fan and installation geometries. Power Balance Method has been applied to compare the power sources and sinks throughout the installation and propulsor for two test cases with different amounts of ingested fuselage boundary layer. The results show that in both cases the severe inlet distortion present at the fan face leads to an 8% drop in fan isentropic efficiency. The test case with a thinner ingested boundary layer was found to generate significantly more dissipation in the development of the boundary layer upstream of the propulsor, in the flow separation over the outer cowl, and within flow separation in the downstream jet. Due to this increase in dissipation, the case with thinner ingested fuselage boundary layer consumes 7% more power relative to the baseline case. This demonstrates the importance of matching the installation with the incoming fuselage boundary layer.