The Effect of Blade Pitch and Reynolds Number on the Performance of Cross-Flow Turbines

Abstract

In this work we studied experimentally the performance of a three straight-bladed Cross-Flow Turbine (CFT) based on symmetric NACA-0015 profiles, with a chord to rotor diameter ratio c/D = 0.16. The fixed pitch angle of the blades of the CFT can be changed, so experiments were carried out with a β = 0° and with a β = 8° toe-out blade pitch. Tests were made in a wind tunnel facility at three different turbine diameter Reynolds numbers in the range ReD = 3 · 105 – 5 · 105. The Tip Speed Ratios (TSRs) covered in the experiments went up to 2.6. Results showed how as the Reynolds number based on the diameter of the turbine, had practically no effects on the performance of the CFT for the experiments conducted with β = 0°, in the case of β = 8° toe-out, the range of ReD covered a transitional region in which the torque produced by the blades overtook the aerodynamic resistive torque imposed by the arms (blade supports) of the CFT yielding high performances for the case with ReD = 5 · 105.