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Aeropropulsive evaluation of boundary layer ingestion for medium electric-powered uavs

Abstract:

The performance benefits of ingesting the boundary layer (BLI), in conjunction with the development of novel aircraft concepts-like the Blended Wing Body (BWB)-have been envisioned with the aim of increasing the aircraft propulsive efficiency whilst reducing the gas emissions in civil aviation. Preliminary studies have shown that BLI can also lessen considerably the takeoff gross weight (TOGW) and the fuel consumption. However, these benefits depends on the incoming flow quality since non-uniform and highly-distorted flows affect severally the performance of the turbomachinery. Moreover, since the BLI technology has not been formally considered in the design of medium UAVs, this work seeks to present a preliminary study regarding the potential benefits of integrating a BWB airframe with three electric ducted fans embedded into the fuselage. For this purpose, the fan thermodynamic behavior is modeled through parametric routines using a propulsor inner-control-volume to determine the effects on the aircraft performance. The flow characteristics, such as the velocity and pressure fields, are obtained from a high-fidelity numerical simulation (at each duct station) carried out in Open Foam. This study used five different inlet topologies to study the suitability of incorporating BLI to medium BWB airframe. Results showed that the low operating Mach and Reynolds numbers do not produce an important effect on the fan performance, since high inlet duct recovery factors are achieved. Furthermore, the three dimensional assessment enables to highlight that the spanwise pressure distribution of the main air frame is not affectted by the incorporation of semi embedded ducts.