Influence of stall fences on the performance of Wells turbine

Abstract

The Wells turbine is one of the candidates for use in Oscillating Water Column (OWC) type wave energy conversion devices. The narrow operating range of a Wells turbine limits its application to a small range of ocean environments. At a high angle of attack, the turbine performance drops suddenly due to a phenomenon known as stall. The present study introduces stall fences in the Wells turbine blade to postpone stall and widen the operating range. The stall fences are defined by the length, height, and thickness in percentage of blade chord length. For the present study, dimensions of the stall fences are determined by using a surrogate-based optimization technique. The modified and reference turbine are numerically studied by solving the Reynolds-Averaged-Navier-Stokes equations in the commercial CFD software ANSYS CFX 16.1. The comparison of fenced turbine with reference turbine shows 16.6% improvement in operating range at the cost of peak torque developed by the turbine. The peak-to-average power ratio in the stall-free range is reduced by 16.7% when stall fences are used. The change in internal flow due to the presence of stall fences is analyzed in detail in the present work.