Numerical Investigation on the Influence of Geometrical Parameters on the Aerodynamic Performance of a Small-Scale Ducted Fans System

Small-scale ducted fans can be used to generate the necessary force and moment for propulsion in many applications. In the present work, the aerodynamic performance of a ducted fans system (DFS), which consists two distinct counter-rotating ducted fans, is analyzed numerically by considering the influence of different geometrical parameters that include rotational speed, eccentricity, and the distance between the two fans. The results reveal that the force and moment in the axial direction are orders of magnitude higher than those in the other two directions under typical conditions. The aerodynamic performance of the DFS shows only minor vibrations for dimensionless rotational speed N below 1 which corresponds to the critical physical rotational speed of 2.10⁴ rpm. Moreover, the force and moment increase dramatically for higher N, following the typical relationship between rotational speed and force for rotor systems. The eccentricity contributes to significant increase in magnitudes on both force and moment in all three directions, whereas the distance between the twin fans exhibits little impact. The numerical simulations suggest that the exploitation of eccentricity is the most efficient approach to control the total output of force and moment of the DFS within the investigated range of geometrical parameters.