Article ID Journal Published Year Pages File Type
1725876 Ocean Engineering 2014 9 Pages PDF
Abstract

•Annual-averaged power obtained from simulations of spar-buoy OWC in Atlantic ocean.•Simulations were based on results from model testing of air turbines.•Blade tip-speed constraints limit Wells turbine performance in energetic sea states.•Several stages required for acceptable aerodynamic performance of Wells turbines.•Biradial impulse turbine performs better than single- and multi-stage Wells turbines.

The OWC spar-buoy is an axisymmetric device consisting basically of a (relatively long) submerged vertical tail tube open at both ends and fixed to a floater that moves essentially in heave. The air flow displaced by the motion of the OWC inner free-surface, relative to the buoy, drives an air turbine. Here, numerical procedures and results are presented for the power output from turbines of different sizes equipping a given OWC spar-buoy in a given offshore wave climate, the rotational speed (maximum allowable blade tip speed of 180 m/s) being optimized for each of the sea states that, together with their frequency of occurrence, characterize the wave climate. Single- and multi-stage Wells turbines and the new biradial impulse turbine were chosen for comparisons. Non-dimensional performance curves of the turbines were obtained from model testing. A stochastic approach was adopted for the hydrodynamic modelling, with air compressibility effects accounted for in a linearized way. The results for the overall performance show that a single-stage Wells turbine would not be a good choice, several stages being required for acceptable performance. The biradial turbine appears as the best choice in terms of performance, with the advantage of substantially smaller rotor diameter.

Related Topics
Physical Sciences and Engineering Engineering Ocean Engineering
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