Measurement of Aerodynamic Passive Twisting in Lattice-Structured Propeller Blades via Wind Tunnel Tests

This research proposes a new passive variable pitch propeller with a lattice structure. Introducing the lattice structure gives a propeller a characteristic that makes it easier to deform in a specific direction. In the proposed propeller, a quasi-cube lattice modified to fit an airfoil shape is used to give the propeller a torsional deformable characteristic, and the goal is to realize a variable pitch mechanism without using a mechanical device. A prototype propeller was created using a 3D printer and evaluated in a torsion test and wind tunnel. Torsion tests revealed that the surface film strengthens the torsional rigidity of the proposed propeller. These results suggest that the film's effect should be considered when designing more sophisticated lattice propellers. Wind tunnel tests confirmed that the prototype propeller was de-formed but not destroyed, and the propeller generated thrust. A high-speed camera photographed the deformation of the propeller and it was observed that the deformation was composed of bending and torsion. The observed maximum torsional angle was about 3º. These results suggest the feasibility of the proposed concept.