Numerical Investigation of High-Lift Propeller Positions for a Distributed Propulsion System

The aerodynamic propeller-wing interactions of a distributed propulsion system in a high-lift scenario were investigated. A 2.5D computational fluid dynamics parameter study with steady-state Reynolds-averaged Navier-Stokes simulations of a wing segment and an actuator disk was conducted to determine the sensitivities and correlations of design parameters at high angles of attack. The parameter study revealed a significant lift augmentation (about +60% at alpha = 6 deg) but a decrease in propulsive efficiency (about -19% at alpha = 6 deg). With increasing angle of attack, the lift augmentation effect decreased (down to about +50% at alpha = 14 deg), whereas the propulsive efficiency decreased further (to about -31% at alpha = 14 deg). The design parameter presenting the largest sensitivity toward system performance was the vertical propeller position. The distance between the propeller and the wing had a comparatively minor effect, as long as the vertical propeller position was adapted accordingly. Propulsive performance could be significantly improved by tilting the propeller downward toward the inflow (by about +30% for theta = 20 deg as compared to a nontilted propeller). A spanwise clustering of propellers (tip-to-tip distance of Delta Y-tip <= 25%D) appears to be beneficial when considering a predetermined amount of distributed propellers.