Date of Award

8-2013

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Michael Peterson

Second Committee Member

Richard W. Kimball

Third Committee Member

Douglas Read

Abstract

This thesis is a summary of testing conducted with a Darrieus style cross-flow tidal turbine. Many locations around the world have locations suitable for tidal turbine energy, including the Cobscook Bay in Eastport, Maine. Cross-flow turbines are likely to have a smaller impact on the environment compared to axial flow turbines due to their operation at lower tip speed ratios. Since very little experimental data is available presently for cross-flow turbines, this study provides an expansive set of performance data for two NACA series blade profiles of the same chord length. One blade profile was used in two different orientations during testing. The University of Maine tow tank was utilized to perform testing in order to determine the peak power coefficient for each blade profile. Tests of two and four blade turbines were conducted at fixed inflow velocity for a range of tips speeds and blade toe angles. Turbine performance was compared to determine the most efficient solidity ratio and profile. Power coefficient curves compared consistently with previously published data. Testing was also performed to determine the effects of viscosity and free surface effects by varying water temperature and water column height on turbine performance. This data was collected with the blade profile that provided the most efficient results set to its optimal toe angle. Results determined that both viscous and free surface interactions had considerable effect on efficiency results.

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