Aerodynamic Performance Benefits of Over-the-Wing Distributed Propulsion for Hybrid-Electric Transport Aircraft

The goal of this study is to analyze how the aero-propulsive benefits of an over-the-wing distributed-propulsion (OTWDP) system at component level translate into an aero-propulsive benefit at aircraft level, and to determine whether this enhancement is sufficient to lead to a reduction in overall energy consumption. For this, the preliminary sizing of a partialturboelectric regional passenger aircraft is performed, and its performance metrics are compared to a conventional twin-turboprop reference for the 2035 timeframe. The changes in lift, drag, and propulsive efficiency due to the OTWDP system are estimated using a simplified numerical method, which is validated with experimental data. For a typical cruise condition and the baseline geometry evaluated in the experiment, the numerical method estimates a 45% increase in the local sectional lift-to-drag ratio of the wing, at the expense of a 12% reduction in propeller efficiency. For an aircraft with 53% of the wing span covered by the OTWDP system, this aerodynamic coupling is found to increase the average aero-propulsive efficiency of the aircraft by 9%, for a 1500 nmi mission. Approximately 4% of this benefit is required to offset the losses in the electrical drivetrain. The reduction in fuel weight compensates the increase in powertrain weight, leading to a take-off mass comparable to the reference aircraft. Overall, a 5% reduction in energy consumption is found, albeit with a ±5% uncertainty due to uncertainty in the aerodynamic modeling.