Performance improvements of vertical axis wind turbines with modified gurney flaps

Abstract

Plain Gurney flap (PGF), as a passive flow control method, is widely used to improve the aerodynamic performance. Due to the drag penalty, a novel serrated Gurney flap (SGF) is proposed. The numerical simulation is carried out to investigate the effects of GFs on the aerodynamic performance of the NACA0018 airfoil and an associated two-blade rotor of a H-type Vertical Axis Wind Turbine (VAWT). The height of GF ranges from 1.5% to 6% of the airfoil chord length. The results show that the SGF doesn’t exhibit the same lift enhancement as PGF, but lower drag. When the flap height reaches 6% c, the SGF airfoil has the higher lift-to-drag ratio. The 3%-chord-length height of GFs is employed on the rotor and it implies that both PGF and SGF can enhance the output power of VAWT. SGF has superior performance than GF, especially at the TSR>2.5 conditions. At the optimal TSR=3.0, the output power of SGF turbine is 2.7% higher than that of PGF one. The highest improvement of power can reach 13.3% at TSR=4.0.