Researchers from the School of Aeronautics and Astronautics at Shanghai Jiao Tong University, including Han Zhen Li, Yu Hu, Lai Zhang, Hong Bo Sun, and Xu Chao Zhang, have been investigating ways to improve the efficiency of cycloidal propellers, which are used in unmanned aerial vehicles (UAVs) and electric vertical take-off and landing (eVTOL) aircraft. Their work, published in the journal Applied Energy, focuses on optimizing the hovering efficiency of these propellers by incorporating end plates.
Cycloidal propellers are valued for their ability to provide thrust in any direction, enabling smooth transitions between hovering and forward flight. However, they typically have lower hovering efficiency compared to traditional screw propellers. The researchers aimed to address this issue by adding end plates to the blade tips, which can reduce blade tip vortices and improve efficiency. Previous studies had not thoroughly examined the impact of these end plates or determined the optimal design for cycloidal propellers.
To optimize hovering efficiency, the researchers conducted extensive force measurement experiments and employed computational fluid dynamics techniques. They found that designs with end plates generally performed significantly better than those without. End plates helped maintain hovering efficiency even with a small blade aspect ratio of 1.5. The study revealed that stationary end plates were more effective than rotating ones, as rotation introduced additional torque due to friction. Additionally, thick end plates outperformed thin ones because their rounded edges eliminated end plate vortices.
The optimal design identified in the study featured stationary thick end plates, a chord-to-radius ratio of 0.65, and a large pitching amplitude of 40 degrees. This design achieved a hovering efficiency of 0.72 with a blade aspect ratio of 3, comparable to that of helicopters. In contrast, the highest hovering efficiency without end plates was merely 0.54. These findings provide valuable insights for improving the efficiency of cycloidal propellers in UAVs and eVTOL aircraft, potentially enhancing their performance and energy efficiency in various applications.
The research was published in the journal Applied Energy, volume 333, on February 1, 2023.
This article is based on research available at arXiv.