DIStributed PROPulsion



The ever-increasing amount of air travel and transport calls for substantial improvements in aircraft fuel efficiency and emissions.  Long term roadmaps such as the ACARE 2020 or the Flightpath 2050 Goals call out specific goals in this direction, which are reflected in the Clean Sky 2 work programme and the goals stated therein. In particular, a 75% reduction in CO2 emissions through 2050 is required to limit the impact of growing air traffic on the global CO2 concentration that is linked to climate change. The challenges for aircraft design became even more intense due to the aim of the European Green Deal to be the first climate neutral continent in 2050. To reach these goals, radically new aircraft technology is required.

Distributed Propulsion (DP) is one such new technology that holds the promise of drastically increasing overall aircraft efficiency and thereby reducing CO2 and other GHG emissions. In contrast to traditional commercial A/C configurations, which are typically powered by two or four engines locally attached to the wing, DP consist of spreading or distributing a larger number of smaller propulsion systems across the wing span.

Distributing the propulsion system of an aircraft using a number of small engines instead of a few large ones has several potential advantages in terms of overall aircraft efficiency as well as noise reduction, safety and reliability, increased affordability, or the ability to introduce more efficient control systems. In addition to this, and in specific relationship with the Clean Sky 2 goals, the two main advantages of distributed propulsion are (1) an increased overall efficiency through favourable interaction between the wing and the slipstream, and (2) the possibility of introducing electric or hybrid- electric propulsion on large transport aircraft because of the use of relatively small engines. Both effects directly increase the fuel efficiency of the aircraft and lead to reduced GHG emissions.

Nevertheless, current aerodynamic and aeroacoustic modelling capabilities are not mature enough to enable satisfactory analysis and design of distributed propulsion for hybrid-electric aircraft yet. This is mostly due to the fact that a DP system will consist of a large number of propellers operating in close proximity to the A/C wing. These so-called propeller arrays will generate a complex slipstream that will interact with the air flow over the wing and affect its aerodynamic and aeroacoustic properties. Current aero analysis and design tools, which have been optimised for classical, large gas-turbine-based propulsion systems, do not incorporate these interaction effects and thus cannot be satisfactorily used as- is on DP aircraft.
Hence, the main objective of DISPROP is to improve the current aerodynamic and aeroacoustic analysis and design capabilities for large aircraft operating with distributed propulsion and propeller arrays.

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