Preliminary Experimental Assessment of the Boundary Layer Ingestion Benefit for the D8 Aircraft

TLDR

The study aimed to quantify the aerodynamic benefit of boundary layer ingestion for the D8 transport aircraft concept via wind tunnel experiments. Two 1:11 scale, 13.4‑ft‑span D8 models—one with BLI and one without—were tested in the NASA Langley 14×22‑ft subsonic wind tunnel, using identical airframes and propulsors, fully tripped, to compare the propulsor power needed to generate a given net stream‑wise force. The experiments demonstrated that BLI propulsors required 6% less electrical power at the simulated cruise point, indicating a measurable aerodynamic benefit for the D8 aircraft.

Abstract

Wind tunnel experiments were performed to quantify the aerodynamic benefit of boundary layer ingestion (BLI) for the D8 transport aircraft concept. Two powered 1:11 scale, 13.4 ft span models, in BLI and non-BLI versions, were tested at the NASA Langley 14⇥22 Foot Subsonic Wind Tunnel to directly compare their performance. The models share the same basic airframe and propulsor units for the most direct comparison. They are also fully tripped to make the measured BLI benefit results scalable to the full-size aircraft. The comparison metric is the propulsor power required to produce a given net stream-wise force on the entire aircraft. The results show that the model BLI propulsors require 6% less electrical power at the simulated cruise point. These experiments provide the first back-to-back assessment quantifying the aerodynamic benefits of BLI for a civil aircraft. The BLI benefit quoted is preliminary in nature because it is defined in terms of electrical power, but we are in the process of obtaining a value in terms of flow power and there is indication that the BLI saving will remain essentially the same.