Experimental Investigation of a New 3d Printed Wells Turbine Under Dynamic Stall Conditions for Wave Energy Conversion

Abstract

Marine energy still plays a marginal role in the global energy scenario, despite the incessant effort by research for more than thirty years in the exploitation of the so-called blue energy. Among the wide range of marine technologies, Oscillating Water Column systems, coupled with Wells turbines, can be considered among the most mature wave energy technology. Wells turbines are affected by dynamic stall, experiencing evident high frequency torque fluctuations which overlay on the typical hysteresis loop, mainly during flow deceleration. These fluctuations are not evident because hysteresis loops are usually provided with phase-averaged data, which can smoothen or even conceal them. This work proposes a new 3D-printed Wells turbine, which was tested in an open wind tunnel to better investigate this phenomenon. As a result, unsteady torque fluctuations occur during the flow deceleration till the flow reattachment. This phenomenon is intensified as the amplitude of the flow rate increases and the wave period decreases. Hence, detecting these oscillations can be relevant in the turbine design phase. Moreover, this unsteady behavior is due neither to the mass flow rate nor to the stagnation pressure drop, but only to the detachment of vortices travelling along the suction side of the blade.

Keywords: Wells Turbine, wave energy, OWC, ocean energy, Marine Energy, Blue economy