Abstract:
This paper focuses on systematic time-averaged performance measurements of a cycloidal rotor operating at Reynolds numbers between 100,000 and 300,000. Cycloidal rotor is a revolutionary horizontal axis propulsion device that has proven to benefit from increased maneuverability and aerodynamic efficiency at micro air vehicle (MAV) scales. The current study aims to characterize the performance of a cycloidal rotor at significantly larger UAV-scales. Towards this, a three-component balance was custom built to measure the vertical thrust, sideward thrust and torque of a 3.5 ft diameter cycloidal rotor. Experiments were conducted for a range of rotational speeds across different blade pitch amplitudes for both 2- and 4-bladed cycloidal rotor configurations. Higher Reynolds numbers associated with operation and a lower chord/radius ratio led to a reduction in the relative magnitude of the sideward thrust when compared to MAV scales and hence, a smaller tilt of the resultant thrust from the vertical. Examination of the effect of blade pitch amplitude showed an optimal pitch amplitude of ±30° for both the 2- and 4-bladed rotor configurations. This optimal pitch amplitude is significantly lower than what was previously determined for MAV scale cycloidal rotors because of the order of magnitude difference in Reynolds numbers. Increasing the number of blades from two to four increased the aerodynamic efficiency for all pitching amplitudes ±25° and higher.