Development of turbines for use in oscillating water columns.

Bidirectional impulse turbines for oscillating water column wave power devices have the inherent problem of pressure losses associated with the outlet guide vane, adversely affecting the performance of the turbine. Two methods of guide vane design have been investigated with the aim of improving the performance of bidirectional impulse turbines by reducing these losses. These methods employ the use of optimisation, using computational fluid dynamics as a method of predicting the performance of the turbine. Numerical results are presented of the performance of the datum turbine, these have been validated using previous experimental data. These results are used as a baseline to measure performance improvements. An optimisation system has been adapted for the guide vanes of the datum turbine, allowing optimisation in bi-directional flows. Two novel guide vane design concepts were explored and the results of parameterisation studies investigating the effects of specific guide vane parameters are presented. The results of two global optimisation procedures, demonstrating the predicted performance improvements of the optimum guide vane configurations are presented. Both optimisation methods demonstrate reduced losses associated with the OGV of the turbine. The second concept, investigating guide vane profile optimisation in bi-directional flows, resulted in a respectable gain in turbine efficiency.