A Solution-based Stall Delay Model for Horizontal Axis Wind Turbines

Open Access
Author:
Dowler, Joshua Lyle
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
January 09, 2013
Committee Members:
  • Sven Schmitz, Thesis Advisor
Keywords:
  • Wind Turbine
  • Aerodynamics
  • Stall Delay
  • Rotational Augmentation
Abstract:
A comprehensive review of contemporary stall delay models and a proposed new solution-based stall delay model to predict rotational effects on horizontal-axis wind turbines are presented. In contrast to conventional stall delay models that correct sectional airfoil data prior to the solution to account for three-dimensional and rotational effects, a novel approach is proposed that corrects sectional airfoil data during a Blade Element Momentum (BEM) solution algorithm by investigating solution-dependent parameters such as the spanwise circulation distribution and the local flow velocity acting at a blade section. An iterative process is employed that successively modifies sectional lift and drag data until the blade circulation distribution is converged. Results obtained with the solution-based stall delay model show consistent agreement with measured data along the NREL Phase VI and MEXICO rotor blades at low and high wind speeds. A final application of the solution-based stall delay model to a notional 2.3-MW turbine design demonstrates the presence of rotational augmentation at inboard stations of utility-scale wind turbine rotors.