Numerical Investigation of Duct Augmented Vertical Axis Wind Turbine With Cambered Airfoils

Abstract

In urban settings, vertical axis wind turbines (VAWTs) have gained recognition for their ease of usage and omnidirectional wind acceptance. Their low efficiency in comparison to horizontal axis wind turbines (HAWTs) has prevented them from being extensively utilized, though. A viable solution to this constraint is duct augmentation, which aims to increase airflow and, consequently, the capacity to harvest energy. This study investigates the integration of a duct in the wind turbine system to enhance the performance of VAWT. This work reports a two-dimensional (2D) numerical simulation of a ducted VAWT using a standard blade profile NACA0017 of National Advisory Committee for Aeronautics (NACA) to evaluate its performance in comparison to that of a bare VAWT. Furthermore, a thorough examination of torque ripple factor, coefficient of power (CP), instantaneous net torque coefficients, wake velocity deficit, turbulent intensity and vorticity distribution surrounding the duct is conducted. While the tip speed ratio (TSR) value for bare VAWT with NACA0017 airfoils corresponding to highest CP is 3, this value shifts to 3.5 when VAWT is augmented with duct. For ducted VAWT, the range of maximum CP is within 0.5 to 0.7 at TSR 3.5. CP is enhanced by approximately 5 times compared to the bare VAWT for inlet velocities V∈[3, 4 m/s]. With increasing wind speed beyond 5 m/s, the CP goes on reducing. The torque ripple factor is found to be lowest at a TSR of 3.5, where the maximum augmentation is achieved.