Tidal Turbine Hub-Blade Connection Design

1. Tidal Turbine Hub-Blade Connection Design Matthew Fowler - Daniel Kittridge – Mark Pemberton – Andrew Litchfield Background Designs Testing T-Bolt Design SeaGen Design On December 11, 2006 Verdant Power installed its first two tidal turbines in the East River of NYC. Shortly after the installation, the strong currents in the east river snapped several of the turbine’s blades. This project set out to try and determine a better hub-blade connection. Our approach was to look to the existing wind turbine technology, which has already proven successful, and adapt their designs for the tidal turbines. By researching various wind turbine hub-blade connections, we were able to come up with several basic connection designs to setup in 3D modeling software In order to test the accuracy of the computer models, several pieces of vinylester composite were loaded using the Advanced Manufacturing Center’s MTS loader. The composite was attached to the I-Frame below and loaded on both ends to failure. Displacement and strain gages were both used to read the material’s response to load. A computer model of the setup was then created and run using the same load parameters to compare with the experimental data. Dual Collar Design Carrot Design The carrot design was rejected as a possible design because the strength of the design depended on the strength of the epoxy on the insert, rather than on the strength of the composite. Results and Conclusions Analysis After completing the FEA analysis with unified dimensions and loads, we were able to determine which design behaved the best under the types of loading that it would be exposed in real world applications. The analysis showed that the T-bolt design behaved the best, yielding the lowest values of stress and strain of the three tested. The next best design was the SeaGen design, which is used by the only commercial scale turbine currently producing power. Lastly, the Collar Sandwich design had the worst test results, having the highest stress concentrations of the three tested. In order for the models to be analyzed using finite element analysis (FEA), the designs made in SolidWorks had to be simplified. This meant cutting a 30 degree section of each connection and importing it into the Abaqus FEA software. The 30 degree sections were then defined with their material properties and loaded with an equivalent force. The stress concentrations you see below are the product of the finite element analysis. SeaGen Design Dual Collar Design T-Bolt Design Based on the results displayed in the chart above, the T-bolt design is clearly the best design for the tidal turbine connection. Also, the T-bolt design has been in use for wind turbines for many years, and has proven itself successful over time. Therefore, our suggestion for an improved hub-blade connection is the T-bolt design. Acknowledgements We would like to give a special thanks Mick Peterson, Senthil Vel, Vincent Caccese, Justin Poland, Keith Berube, Raul Urbina and Steven Blake, and the AMC for all the help they have given us throughout our design project.