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Numerical modelling techniques to predict rotor imbalance problems in tidal stream turbines

Ordonez-Sanchez, Stephanie, Porter, Kate, Ellis, Robert, Frost, Carwyn ORCID:, Allmark, Matthew ORCID:, Nevalainen, Tomas, O'Doherty, Timothy ORCID: and Johnstone, Cameron 2017. Numerical modelling techniques to predict rotor imbalance problems in tidal stream turbines. Presented at: 12th European Wave and Tidal Energy Conference (EWTEC), Cork, Ireland, 27 August - 1 September 2017.

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Load fluctuations caused by the unsteady nature of tidal streams can have severe impacts on turbine components. As seen in the wind industry, turbine blades can become misaligned due to a fault in the pitch mechanism or blade deformations arising over time. These misalignments will represent a loss of power capture and perhaps even premature failure of the components if not detected in time. Computational fluid dynamic (CFD) techniques can be used to predict the performance of a turbine with a misaligned blade. However, these numerical modelling techniques quickly become computationally expensive when modelling realistic, time-varying conditions. Blade Element Momentum Theory (BEMT) offers a quicker and simpler approach, although with several limitations. In this paper BEMT is adapted to predict the performance of a three bladed tidal turbine with one or two blades offset from the optimum pitch setting. This approach is compared with a CFD model to study the effectiveness of both methods to predict power and thrust when a rotor blade has an offset. The simulations were undertaken at three flow speeds (0.9, 1.0 and 1.1 m/s). Both numerical models are compared to experimental data that was obtained at a flume tank in similar flow conditions. The results showed that both BEMT and CFD are able to predict power coefficients when there is a small offset of one rotor blade. However, the predictions were poorer when two blades had two different offsets at the same time.

Item Type: Conference or Workshop Item (Paper)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Funders: EPSRC
Related URLs:
Date of First Compliant Deposit: 10 October 2017
Last Modified: 03 Nov 2022 09:32

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