Design Improvement of a Distributed Propulsion System in Cruise Using Numerical Simulations

Distributed propulsion (DP) systems are known for their lift augmentation capabilities in high-lift conditions, although their propulsive efficiency in cruise is lower. This paper evaluates different measures aimed at increasing the aerodynamic and propulsive efficiencies of a DP system. The wing of a generic regional aircraft with a DP configuration and a nacelle is taken as the baseline. Lightly loaded propellers that result in poor propeller performance in cruise flight, as well as nacelle interference effects, are observed. Design parameters that strongly affect propeller performance in a tractor configuration with a nacelle are shown. Propeller–wing integration aspects (such as the propeller inclination angle) are exploited to increase propulsive efficiency by 9.3 points. Aerodynamic efficiency is increased by reducing drag by 23.6% using numerical simulations with the DLR TAU code. Vortex interactions in the streamwise direction are investigated. Vorticity around the nacelle builds up and interacts with the horseshoe vortices, where it significantly affects the flowfield by changing the local shape factors and causing separation pockets.