Wave energy harvesting impulse turbine having ring type blade: Experiments with unsteady flow

Oscillating water column (OWC) wave energy converters employ air turbines coupled with an electrical generator to convert the wave energy into electrical energy. In the present study, a ring-type axial flow impulse turbine of diameter 196 mm was manufactured to carry out the experiments in an unsteady flow test rig. The tests were done for the stroke lengths (SL) of 0.2m, 0.3m, and 0.4m, and the periods (TP) varied from 6 to 12 s. A rheostat was connected to the generator, and the turbine pressure drop and power output variations were recorded for different generator loading conditions. The flow rates for the exhalation phase were measured and time-series analysis of the pressure drop and rotor speed was done. A suitable resistive load was found out for obtaining the highest power output. A relationship between average power and average pressure drop was established. Furthermore, a relationship was established between the turbine pressure coefficient and the turbine power coefficient. Lastly, a study on damping characteristics of the turbine was also done to study the effect of damping on the turbine's overall performance. •An experimental analysis for unsteady flow through an Impulse turbine for OWC.•A ring-type rotor turbine was designed and tested in the laboratory.•Loads to the generator was optimized for maximum power output.•Pressure coefficient, power coefficient, and damping coefficient were studied for different conditions.