Performance of a Cycloidal Rotor Concept for Micro Air Vehicle Applications

The viability of a cyclorotor for powering a hover-capable micro air vehicle (MAV) was examined by making performance and flow field measurements. Parametric studies were conducted to determine the dependence of performance on rotational speed, the amplitude of the blade pitch, the blade airfoil shape, and blade flexibility. All of the experiments were conducted using a three-bladed cyclorotor system, which was built light enough to be used on an actual flight-capable MAV. While higher blade pitch angles were found to improve performance and increase the power loading of the cyclorotor, significant bending and torsional flexibility of the blades had a deleterious effect on performance. Blade section camber also proved to be detrimental to overall performance. Force measurements showed the presence of a significant sideward force on the cyclorotor (along with the vertical thrust force), analogous to that found on a spinning circular cylinder. Particle image velocimetry (PLY) measurements made in the wake of the cyclorotor provided evidence of a significant wake skewness, which was produced by the sideward force. The thrust produced by the cyclorotor was found to increase until a blade pitch angle of 45 degrees was reached without showing any signs of blade stall. This behavior was also explained using the PIV measurements, which indicated evidence of a stall delay as well as possible increases in lift on the blades from the presence of a leading edge vortex.