Effect of Taper Distribution on the Torque and Thrust Generated by a Wind Turbine Rotor Blade

Abstract

The effect of taper distribution along the span of a wind turbine rotor blade is analyzed in terms of the thrust and the torque. Taper distribution is expressed as a cubic spline defined by three chord lengths values in the spanwise direction: root, mid-span and tip. Various chord length values are investigated. The Reynolds Averaged Navier-Stokes computations are done using a commercial solver. The k-epsilon turbulence model is used to calculate the eddy viscosity. The baseline rotor blade is selected as the NREL phase VI blade. Different blade shapes were generated by setting different chord length values at the specified three spanwise locations for the same planform area as the baseline blade. Increasing torque and decreasing thrust cases are observed. It is noticed that torque increases when the tip chord length is reduced as one fifth/sixth of the root and mid-span chord length. The thrust is decreased as the root chord is much longer than the mid-span and the tip chord.