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Recent studies have proposed using Boundary Layer Ingestion propulsion systems utilizing turboelectric generators to increase fuel efficiency in the next generation of airliners. Another aircraft platform where fuel savings would be highly valuable would be long-range UAVs. Therefore, a design optimization study was conducted on a BLI propulsor for an adaptation of a RQ-4 Global Hawk airframe, which is an airframe that is already proven to be ideal for long range missions. The study was performed on STAR CCM+ CFD software, using the Design Manager feature within the program. The interest was in optimizing the propulsor for cruise conditions, when the fuel savings will be most valuable in achieving a longer range. An initial simulation was performed, to act as the reference simulation for the Design Manager study. After initial values were obtained, the Design Manager study was conducted in two different iterations, searching for the ideal design. A variety of geometric variables were input into the Design Manager, such as inlet and outlet cross-sectional area, and the shape of the inner engine. Upon completion of the study, an ideal design of a BLI propulsor was found. The total power necessary to achieve static equilibrium flight was reduced from 222 MW to 193.2 MW, a savings of 12.87%. Such power savings are significant considering that a BLI propulsor already achieves fuel savings compared with a traditional propulsor that ingests air traveling at the free stream velocity. This study acts as a rationale for the further development of a physical scale model to validate such results, and the possibility of commercial development if satisfactory results are obtained.

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Design Optimization of a Boundary Layer Ingestion Propulsion System for a Long-Range, High-Altitude UAV

Recent studies have proposed using Boundary Layer Ingestion propulsion systems utilizing turboelectric generators to increase fuel efficiency in the next generation of airliners. Another aircraft platform where fuel savings would be highly valuable would be long-range UAVs. Therefore, a design optimization study was conducted on a BLI propulsor for an adaptation of a RQ-4 Global Hawk airframe, which is an airframe that is already proven to be ideal for long range missions. The study was performed on STAR CCM+ CFD software, using the Design Manager feature within the program. The interest was in optimizing the propulsor for cruise conditions, when the fuel savings will be most valuable in achieving a longer range. An initial simulation was performed, to act as the reference simulation for the Design Manager study. After initial values were obtained, the Design Manager study was conducted in two different iterations, searching for the ideal design. A variety of geometric variables were input into the Design Manager, such as inlet and outlet cross-sectional area, and the shape of the inner engine. Upon completion of the study, an ideal design of a BLI propulsor was found. The total power necessary to achieve static equilibrium flight was reduced from 222 MW to 193.2 MW, a savings of 12.87%. Such power savings are significant considering that a BLI propulsor already achieves fuel savings compared with a traditional propulsor that ingests air traveling at the free stream velocity. This study acts as a rationale for the further development of a physical scale model to validate such results, and the possibility of commercial development if satisfactory results are obtained.