Researchers from the University of Oxford have been investigating the impact of blade camber on the performance and loading of cross-flow turbines, a type of renewable energy technology that can harness power from both wind and tidal sources. Their findings, published in the journal Renewable Energy, offer valuable insights for the energy industry, particularly in the design and optimization of cross-flow turbines.
Cross-flow turbines, unlike traditional wind turbines, have blades that rotate on an axis perpendicular to the flow of the fluid (wind or water). This unique design leads to a phenomenon known as virtual camber, where the blades’ curvature in the rotating reference frame alters their lift, drag, and pitching moment. The researchers aimed to understand how adding geometric camber to the blades would affect their performance and loading.
The study compared three types of blades: symmetrical (NACA 0018), concave-in (NACA 2418), and concave-out. The concave-in blades, which curve inward, were found to slightly improve the performance of symmetrical blades by enhancing downstream flow reattachment. This improvement more than compensated for the reduced peak power generation. On the other hand, concave-out blades, which curve outward and enhance virtual camber and lift in the power stroke, exhibited sub-optimal performance.
One of the most significant findings was that concave-in blades reduced peak loading by 13%. This reduction could be critical in future designs, especially at high tip-speed ratios, as it could lead to more durable and efficient turbines. The researchers also noted that the influence of geometric camber is non-linear and that the simplistic summation of both geometric and virtual camber may not accurately account for camber effects.
The study’s findings suggest that a small but positive total camber (geometric plus virtual) is optimal for the turbine design used in this research. This insight could guide the design of more efficient and durable cross-flow turbines, contributing to the advancement of renewable energy technologies. The research was published in the journal Renewable Energy, providing a valuable resource for engineers and researchers in the energy sector.
This article is based on research available at arXiv.