Radial impulse turbines could be a good option in Oscillating Water Column systems to extract energy from waves. A previous work made by the authors showed that the tip clearance plays a fundamental role in the flow pattern inside the turbine, so seeing the relation between tip clearance’s size and turbine performance is a very interesting issue from the point of view of designing this kind of turbomachine.
Evaluate the tip clearance influence on the turbine performance is the purpose of this work. The geometry proposed in (1) with different tip clearance’s size and the numerical model described in (2) have been used. The performance comparison shows that changing the tip clearance’s size in a 4% of blade span reduces the stationary turbine efficiency up to 9%. Although, the influence of the tip clearance in this geometry is not the same in both flow directions, the efficiency reduction is more pronounced when the flow is centripetal.
From a point of view of manufacturing, to decrease the tip clearance has a limit. Therefore a new turbine design that minimizes the tip clearance effects is proposed. The numerical model is used to evaluate the performance of the new turbine.