Date of Award

Spring 5-6-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Advisor

Richard Kimball

Second Committee Member

Andrew Goupee

Third Committee Member

Lauren Ross

Abstract

This thesis presents the development of a 1/70th scale performance-matched wind turbine intended for wind and wave basin model testing of commercially viable floating wind turbine structures based off of the International Energy Agency (IEA) Wind 15 MW design. The focus of this demonstration is to test active blade pitch response controls and to provide an experimental dataset for use by modelers and industry for future turbine improvements. Future research is planned to test the turbine in conjunction with an actively damping hull to test the interactions between the two control systems.

Outlined in this thesis are the methods of scaling, designing, manufacturing, and testing the scale model. A discussion of the scaling methodology for aerodynamic properties of the blade at model scale Reynolds number is included, as is the Froude scaling methodology used for most other turbine properties. The performance-match target properties are met by scaling the turbine rotational speed following the Froude scaled method, and increasing the test wind speed by approximately 20%, resulting in a mismatch of the tip speed ratio (TSR) between full and model scale in order to preserve the rotor rotation speed Froude scaling, ensuring proper frequency of the turbine forces felt by the hull in comparison to the waves. Scaled mass targets for the nacelle and blades necessitated the incorporation of alternative materials such as carbon fiber and foam into the component designs to lower the weight of the system.

Design of turbine components focused on the integration of all needed sensing equipment into the tower top nacelle as well as designing mechanisms to allow for individual active blade control, entirely housed in the hub. High-density foam molds were manufactured for the production of carbon fiber blades through a vacuum infusion process using a modified butterfly blade construction method designed to accommodate the size and complexity of the geometry. A process was created to align and assemble the blade flanges, foam spars, and the two-part carbon fiber skins. Additional manufacturing was done to produce and assemble parts for the nacelle and hub.

Testing of the scale model turbine structural properties included blade deflection testing, dynamic inertia testing of blades, and free-decay testing of the tower's natural frequency. Testing of the turbine performance was conducted in a uniform wind environment over a range of rotor speeds and blade pitches to measure the thrust and torque reactions in each case. This information was used to produce coefficient of power and coefficient of thrust curves versus the rotor tip speed ratio. Additional controller tests were performed to validate the rotor controller’s response to torque feedback in order to optimize the rotor performance in dynamic-wind environments.

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