Computational investigation of the sensitivity of spoiler attachment on wind turbine blades

Wind turbine blades often experience flow separation in the root section of the blade at high wind speeds which consequently reduces power output. In this work, we perform studies to quantify the feasibility and benefit for attaching a spoiler mechanism at the root section of the wind turbine blade. First, a combination of two dimensional computational fluid dynamics analysis and a blade-element-momentum theory based design code is utilized to demonstrate possibility of power enhancement at higher, post-stall wind speeds using a fixed-angle spoiler. These studies are then corroborated using a full three-dimensional computational fluid dynamics analysis. It was observed that fixed-angle spoiler did cause detrimental power loss at lower wind speeds. Coupled fluid/structure analysis of a self-aligning spoiler is performed next to explore the possibility of mitigating this power loss at low wind speeds while still maintaining the power enhancement shown at the higher speeds. Several parametric studies varying design parameters such as spoiler size, attachment location and pre-deployment angle are performed. Finally we show that the optimal self-aligning spoiler identified by this process is able to produce approximately 2:75% improvement in the total power production at the highest wind speed, with minimal power losses sustained at lower wind speeds. Although the observed power enhancements are relatively modest, the concept of a self-aligning spoiler is compelling because of the relative ease and lower cost of implementing the technology on existing wind turbines compared to active control solutions.