A Twin Impulse Turbine for Wave Energy Conversion-Effect of Notch on the Rotor Suction Surface

摘要

The twin impulse turbine topology is used in the oscillating water column system for wave energy conversion.In this topology, there are two unidirectional impulse turbines which have high efficiency in the forward flow and a large flow resistance in the reverse flow.As a principle of the topology, oscillating airflow leads to the forward turbine by the difference of flow resistance between the forward and reverse turbines.Our previous studies showed that the efficiency of the topology was lower than that of unidirectional impulse turbine because of an inflow into the reverse turbine.On the other hand, it is known that the suction surface of rotor has a large effect on the flow resistance of the impulse turbine.It indicates that if we can modify the suction surface so that it can make more flow resistance in the reverse flow and it can finally be improve the rectification performance of twin impulse turbine.The effect of notch on the blade suction surface on the performance of twin unidirectional impulse turbine was investigated by computational fluid dynamics (CFD) analysis.The commercial CFD software of SCRYU/Tetra of Cradle Co.Ltd.was used in the present numerical work.The SST k-ω model was used as a turbulence model.The rotor with notch used in the present study showed larger flow resistance than that of the conventional rotor over a wide range of flow coefficients in the reverse flow.The kinetic energy of flow is lost due to the notch by the collision of airflow.The efficiency in the forward flow is lowered than that of the conventional rotor because of the flow separation in the notch, though the decrease in the efficiency is very low.