A novel axial flow self-rectifying turbine for use in wave energy converters

Abstract

Self-rectifying turbines capable of operating in bidirectional flows are extensively used in Oscillating Water Column (OWC) prototypes, because of their simple structure and low maintenance rate. A new axial flow self-rectifying turbine for reciprocating flows is proposed in this paper. The turbine has a rotor with fan blades, which are set on the hub by a pivot equipped near the leading edge and are free to oscillate between two preset angles determined by mechanical stops. Two rows of guide vanes are symmetrically distributed on both sides of the rotor. The torque equation of the turbine was derived by the law of conservation of momentum under steady flow conditions, and the correctness and effectiveness were verified by numerical simulation. Given the rotor blade rotational angle and guide vane angle as the design variables, and the turbine efficiency as the objective function, a structural optimization problem was solved. The dimensionless coefficients of the optimized turbine were compared with those of the reference design. Theoretical analysis and simulation results indicate that the optimized turbine has less energy loss on the downstream guide vanes and is more efficient when the flow coefficient is large.