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.
|Publication status||Published - 28 Aug 2017|
|Event||12th European Wave and Tidal Energy Conference - University College Cork, Cork, Ireland|
Duration: 27 Aug 2017 → 1 Sep 2017
Conference number: 12
|Conference||12th European Wave and Tidal Energy Conference|
|Period||27/08/17 → 1/09/17|
- numerical modelling
- rotor imbalance
- tidal stream turbine
Ordonez Sanchez, S. E., Porter, K., Ellis, R., Frost, C., Allmark, M., Nevalainen, T., O’Doherty, T., & Johnstone, C. (2017). Numerical modelling techniques to predict rotor imbalance problems in tidal stream turbines. Paper presented at 12th European Wave and Tidal Energy Conference, Cork, Ireland.