Aircraft System Study of Boundary Layer Ingesting Propulsion

A trade-factor-based system study has been carried out to identify fuel burn benefits associated with boundary layer ingestion (BLI) for generation-after-next (N+2) aircraft and propulsion system concepts. The analysis includes detailed propulsion system engine cycle modeling for a next-generation, Ultra-High-Bypass (UHB) propulsion system with BLI using the Numerical Propulsion System Simulation (NPSS) computational model. Cycle modeling was supplemented with one-dimensional theory to identify limiting theoretical BLI benefits associated with the blended wing body reference vehicle used in the study. The system study employed low-order models of engine extractions associated with inlet flow control; nacelle weight and drag; fan performance; and inlet pressure losses. Aircraft trade factors were used to estimate block fuel burn reduction for a long-range commercial transport mission. Results of the study showed that a 3-5% BLI fuel burn benefit can be achieved for N+2 aircraft relative to a baseline high-performance, pylon-mounted, UHB propulsion system. High-performance, distortion-tolerant turbomachinery, and low-loss, low-drag inlet systems, were identified as key enabling technologies. Larger benefits were estimated for N+3 configurations for which larger fractions of aircraft boundary layer can be ingested.