Aerodynamic performance prediction of NREL phase VI blade adopting biplane airfoil

The NREL Phase VI wind turbine is taken as an example to study the changes in aerodynamics performance and 3D flow structures due to the adoption of the biplane airfoil in the inboard region of the blade. The NREL Phase VI blade is taken as the baseline blade, and the biplane blades are designed by replacing the original inboard region with biplane airfoil. The flows around the blades are simulated by solving the Reynolds averaged Navier-Stokes equations with the Spalart-Allmaras model. Results show that evident performance improvement of biplane blades compared with baseline blade. The rotor flap moment to shaft torque ratios of the biplane blade drop, which proves its applicability in large blades. Detailed analysis of sectional loads along the blades further reveals that the increment in shaft torque of the biplane blades mainly comes from the inboard region, and the gap and stagger of the biplane airfoil have pronounced effects on the performance and flow structures of biplane blades. The biplane blades show a good capacity in suppressing flow separation and radial flow. In addition, the transition section from the biplane airfoil to monoplane airfoil must be carefully designed using 3D simulation approaches to reduce its negative effect. (C) 2020 Elsevier Ltd. All rights reserved.