Performance characterization of a wells turbine under unsteady flow conditions

Abstract

In the open wind tunnel of the Polytechnic University of Bari a new 3D-printed prototype of a Wells turbine is investigated under steady-state and pulsating flow conditions. The flow rate is modified by changing sinusoidally the frequency of the control drive, hence 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.