Numerical Investigation of Aeropropulsive Coupling Effects of Distributed Propulsion Systems under Near-Stall Conditions

Abstract

Distributed propulsion (DP) systems offer increased lift, decreased drag, higher propulsion efficiency, and reduced fuel consumption. However, complex aeropropulsive interactions can significantly affect the aerodynamic performance of distributed propulsion systems, particularly under near-stall conditions. To examine the aeropropulsive coupling effects of distributed ducted fans under near-stall conditions, an overwing configuration with an array of five ducted fans was numerically simulated based on a newly developed body force model (BFM). It is found that the suction capacity of the middle fan is markedly weakened as the wing approaches the stall angle of attack (AoA), resulting in markedly lower aerodynamic performance. However, the suction capacity of the edge fans is relatively strong, with only a slight reduction in the aerodynamic performance. Relative to the edge fan, the middle fan exhibits reductions in mass flow rate and thrust of up to 26% and 46%, respectively. As the stall AoA of the wing approached, the middle fan experiences the highest total pressure distortion but the lowest swirl distortion, whereas the edge fans exhibit the opposite trend. The largest discrepancy in total pressure distortion between the middle and edge fans amounts to 26%, while it raises to 66% when discussing the swirl distortion coefficient. At the ducted fan inlet, swirl below 0.8 span of the blade forms in local symmetric vortices, whereas swirl near the blade tip develops into local asymmetric vortices with an increase in the AoA. These findings provide valuable insight into the integrated design of distributed propulsion systems under off-design conditions.