Performance characterization of a Wells turbine under unsteady flow conditions

A small prototype of a Wells turbine has been built by means of 3D printing technology and tested in the test rig facility of the Polytechnic University of Bari under steady-state and pulsating flow conditions. The Wells turbine is crossed by an unidirectional air flow rate that is varied from zero to the maximum by precisely controlling the rotational speed of the suction fan. The Wells turbine is a scaled prototype designed to operate in a 1:10 scaled model of a REWEC3 breakwater for ocean application. The Wells turbine characteristics are evaluated in terms of torque coefficient and pressure drop coefficient vs. flow coefficient. A delayed onset of stall can be observed, with a clockwise hysteretic loop, when the turbine experiences large sinusoidal variation of the flow coefficient at high mass flow rates. The variation of the turbine performance under dynamic flow conditions is crucial for a correct design of the Wells turbine.