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A review of synergistic propulsion-airframe integration

More closely integrated propulsion systems may be a promising avenue towards significant improvements in aircraft energy efficiency. Expected synergy effects cover various disciplines, such as aerodynamics, propulsion, structures, and flight controls. In this respect, the principles of boundary layer ingestion and wake filling have been identified as particularly interesting. An artist view of Bauhaus Luftfahrt’s Propulsive Fuselage concept featuring turbo-electric drive for the aft-fuselage propulsion system is shown in the figure top right.

Bauhaus Luftfahrt has also analysed recently published concepts targeting such synergistic propulsion-airframe integration. The surveyed concepts ranged from unmanned vehicles to long-range blended wing body layouts. The figure bottom right illustrates the growing attention devoted to realising a more closely integrated propulsion-airframe arrangement, especially in the most recent timeframe. It can be concluded that, for small aircraft types, fully or hybrid-electric propulsion is in the focus of many investigations, as aircraft with shorter design ranges may benefit more compared to larger types. However, even for long-range aircraft, a gradual departure from the purely mechanical drive train is noticeable. Also shown is the payload range energy efficiency (PREE) of the concepts. The figure is supplemented with contours of the payload-to-energy mass fraction. It is visible that, for most screened concepts, the synergistic combination of aerodynamic advances, weight reduction technologies, and power plant efficiency enhancements allows for substantial benefits in PREE as well as increased values in the payload-to-energy mass fraction.

  • Propulsive Fuselage concept: An example for a promising approach for synergistic propulsion integration, realised through boundary layer ingestion and airframe wake fillingPropulsive Fuselage concept: An example for a promising approach for synergistic propulsion integration, realised through boundary layer ingestion and airframe wake filling
  • Evolution and potential of highly integrated concepts: Progression of synergistic propulsion integration research (left) and assessment of the integrated performanceEvolution and potential of highly integrated concepts: Progression of synergistic propulsion integration research (left) and assessment of the integrated performance