Aerodynamic performance of distributed electric propulsion with wing interaction

Distributed electric propulsion (DEP) uses multiple propellers driven by motors distributed along the leading edge of the wing to produce beneficial aerodynamic interactions. However, the wing will be in the sliding flow of the propeller and the lift and drag characteristics of the wing will change accordingly. The performance of the propeller will also be affected by the wing in its rear. In this paper, combined with wind tunnel tests, the low Reynolds aerodynamic properties of multiple DEP structures are numerically simulated by solving the Reynolds averaged Navier-Stokes (RANS) equation of multiple reference frames (MRF) or slip grid technology. The results demonstrate that the lift and drag of DEP increase in all cases, with the magnitude depending on the angle of attack (AOA) and the relative positions of propellers and wing. When the AOA is less than 16 degrees (stall AOA), the change of lift is not affected by it. By contrast, when the AOA is greater than 16 degrees the L/D (lift-to-drag ratio) of the DEP system increases significantly. This is because the propeller slipstream delays laminar flow separation and increases the stall AOA. At the same time, the inflow and the downwash effect, which is generated on both sides of the rotating shaft, result in the actual AOA of the wing being greater than the free flow AOA with a fluctuation distribution of the lift coefficient along the span. Also, for the propeller in the DEP, the blocking effect of the wing and the vortex of the trailing edge of the wing result in a significant increase in thrust.