Effects of Propeller Size and Position on the Performance of a UAV Wing in a Distributed Propulsion System

Abstract

Distributed propulsion (DP) systems have gained attention in the design of unmanned aerial vehicles (UAVs) for their potential to enhance flight performance and operational versatility. By dividing thrust generation across smaller distributed propellers positioned along the wing, these systems enhance aerodynamic performance, particularly during low-speed operations such as takeoff and landing. Although DP systems primarily enhance lift during critical flight phases, their contribution to aerodynamic efficiency during cruising is less pronounced. This study provides a detailed examination of the aerodynamic effects of propeller size and elevation in DP systems during climbing, cruising, and transitional phases through numerical simulations. Employing both structured and unstructured meshes, along with a sliding mesh technique for propeller rotation, the shear stress transport (SST) k-ω model is adjusted and validated against experimental data to enhance simulation accuracy. Findings revealed that although DP systems increase lift coefficients, they also elevate drag coefficients, leading to a net reduction in the lift-to-drag ratio. Notably, smaller propeller sizes demonstrated improvements in lift-to-drag ratio compared with the baseline wing configuration. To optimize the system’s performance, particular emphasis is placed on raising the leading-edge propellers three-quarters of the propeller radius above the airfoil. This adjustment accelerates the propeller slipstream above the upper airfoil surface, enhancing overall aerodynamic efficiency.