Test results of a novel twin-rotor radial inflow self-rectifying air turbine for OWC wave energy converters

摘要

The paper presents an experimental study of a novel self-rectifying twin-rotor air turbine to equip an oscillating water column wave energy converter. The turbine is based on a pair of conventional radial inflow rotors mounted on a common shaft, complemented by the corresponding inlet guide vane rows, by a curved-duct manifold arranged circumferentially in a periodic manner and by an axially-moving cylindrical valve. The valve ensures that the air flows alternately through one or the other of the two parts of the twin-rotor turbine, depending on the sign of the pressure head. Due to its symmetry, only one half of the twin-rotor turbine was constructed and tested in a relatively large-scale unidirectional flow at the blow-down test rig of Institute Superior Tecnico. Results are presented in dimensionless form for efficiency, power output, pressure head and flow rate. A comparison with self-rectifying turbines commonly used in wave energy converters is shown. Additionally, an approach of turbine efficiency in random waves was made using the stochastic model. (C) 2018 Elsevier Ltd. All rights reserved.