Thrust Characteristics of Cycloidal Propeller and Flow Measurement

Abstract

Now airships are expected to be used as drones for support services at disasters and global environment monitors. However, such applications have not been successfully attained due to the vehicle’s poor kinetic performances. Our team, then, tries to improve the kinetic performances of airships by installing cycloidal propellers which can instantly change thrusts toward arbitrarily directions by controlling attack angles of the rotor blades. In this study, we report results of static thrust measurement experiment of a cycloidal propeller for 10-meter class airships, and wind tunnel tests and flow measurements around a rotor by the particle image velocimetry (PIV) applying to a miniature cycloidal propeller. The radius of rotor, the chord and the span of blades, the number of blade of the cycloidal propeller for 10-meter class airships are respectively 0.4m, 0.3m, 0.5m, and 3, and those values for the miniature cycloidal propeller are respectively 0.16m, 0.12m, 0.2m, and 3. Firstly it was found that the cycloidal propeller for 10-meter class airships can generate 50N as the maximum thrust at a rotational speed of 8 rps and with attack angle of 25 degrees. Moreover, thrust directions deviate from instructed directions toward the rotational direction by 25 degrees at the maximum. Secondly, from the wind tunnel test, thrust coefficients were found to be decreasing as advance ratios increase, which corresponds to a tendency of general type propellers. In addition, it was clarified that the propeller intakes the air not only from the rotating surface of the propeller but also from the rotor axial direction of the propeller by visualizing the air flow around the rotor by PIV.