Numerical Investigation on the Aerodynamic Performance of Vertical Axis Wind Turbine with the Half-airfoil Wind Collector

In an effort to boost the aerodynamic performance of vertical axis wind turbines (VAWT), a half-airfoil wind collector structure is proposed, inspired by the contour shape of NACA airfoils. To explore the influence of the half-airfoil wind collector on the performance of VAWTs, an optimization design of the half-airfoil wind collector structure is conducted using the Design of Experiments (DOE) method. Based on the NACA0021 airfoil, simulations of computational fluid dynamics (CFD) are used to examine the instantaneous torque, power coefficient, overall torque, and dynamic flow field of the VAWT blades under the influence of the half-airfoil wind collector. The findings reveal that the half-airfoil wind collector has a good wind-collecting effect, effectively guiding the airflow to concentrate on the blades, increasing the local airflow velocity over the blades, and strengthening the differential in pressure between the blades' inner and outer surfaces. This results in an increased torque on the blades and lessens losses related to the enlargement and detachment of dynamic stall vortices. Consequently, the power coefficient of the VAWT is augmented within the scope of high tip - speed ratio. Specifically, When the tip-speed ratio is 3.08, with geometric parameters of x = 0, d = 29c, α = 5°, and the NACA0021 contour, the highest power coefficient reaches 0.59, showing an improvement of 55.8% over the standard VAWT. When the tip-speed ratio rises, the half-airfoil wind collector maintains a high power coefficient and torque coefficient, demonstrating that it enables the VAWT to operate more efficiently at higher rotational speeds, thus expanding the operational range.