Noise assessment of a self-rectifying axial-flow impulse air turbine: A multi-component experimental analysis

Oscillating water column (OWC) wave energy converters employ air turbines, air valves, and electrical generators to convert the energy within the pneumatic chamber into electricity. The selection of the air turbine type depends on the hydrodynamic characteristics of the OWC and the wave resource at the deployment site. Existing research primarily addresses energy production, while future deployments require multi-criteria analyses that include noise emissions. Few studies offer comprehensive analyses of noise emissions under varying load conditions, and most focus on Wells turbines rather than impulse turbines. This study presents an experimental assessment of noise emissions from multiple components of an axial-impulse turbine designed for OWC applications, complemented by measurements of the aerodynamic flow field. Within the range of turbine rotational speeds examined, results indicate that the outlet stator is the primary source of noise. Noise from the inlet stator is negligible compared to that produced by the turbine-generator assembly within the operational flow coefficient range of interest. Noise scaling laws are proposed for integration into wave-to-wire models.