New Nature-Inspired Cycloidal Propeller for Low-Reynolds- Number Hovering Flight

摘要

A new type of pivoting-blade cycloidal propeller, which can equip aircraft with vertical take-off and landing capability, is presented in this paper. This propeller has the appearance of damselfly wings and the advantage of low mass compared with other types developed to date. The operating mode shows similarities with the movement of these insects' wings to generate upward vertical thrust. To cover the range of Reynolds number from 2250 to 25,000, propellers with 70 and 200 mm blades were constructed. Using the blade element theory, a simplified two-dimensional mathematical model was developed to predict thrust, power, and hovering efficiency. Experiments were performed to validate that model for the case of hovering flight. Quantitatively, the results of the experiments match the prediction produced by the two-dimensional mathematical model very well. The theoretical analysis proves that both lift and drag contribute to the net vertical force, and the contribution of drag is at least 50%. This way of generating vectored thrust is emerging as an alternative solution to other types of propulsion in low-Reynolds-number regimes with a blade tip Mach number not greater than 0.2.