EFFECT OF DESIGN PARAMETERS ON AERO-ACOUSTIC AND AERODYNAMIC PERFORMANCE OF WELLS TURBINES

A Wells turbine is an axial turbine, which is capable of extracting energy from an oscillating airflow. In an oscillating water column (OWC) power plant the Wells turbine is operated along its complete characteristic curve from no load to overload and back. Not only maximum efficiency but also damping, pneumatic power, overload capacity and noise emission are crucial parameters which need to be taken into account when designing a turbine for an OWC system. Based on a classical blade element approach a number of rotors were designed varying the hub-tip ratio and the solidity systematically. Three-dimensional numerical RANS simulations are carried out to predict the characteristic curves and extract the optimum operating coefficients as well as the stall margin. Selected rotors are manufactured as scaled down models. A steady state test rig, equipped with highly efficient silencers to ensure low noise air supply, is used to measure the complete aerodynamic and aero-acoustic characteristic curves. The results indicate how the turbines' performance is affected by the choice of the hub-tip ratio and solidity.