Performance evaluation of a downwind diffuser on vertical axis wind turbine

Abstract

Research has proven that the performance of a horizontal axis wind turbine (HAWTs) can be increased significantly by the application of a diffuser. It serves as a power augmented feature to draw higher wind flow toward the HAWT. However, research on integrating a diffuser onto vertical axis wind turbines (VAWTs) is scant, where most of the available power augmentation devices used for VAWTs are the convergent duct, deflector plate, shroud, and guide vanes which are placed in a proper configuration at the upwind. In this paper, laboratory tests and computational simulations have been carried out to study the impacts of a downwind diffuser on the performance of a VAWT. The diffuser is designed with the absence of a concentrator or flange and is placed downwind of the VAWT. Parametric computational fluid dynamics (CFD) studies were carried out for the downwind diffuser length and semi-opening angle. A five-bladed H-rotor was selected as the testing wind turbine, whereas the diffuser used was made up of flat plates. Both simulations and experiment results are consistent. From the experiments, it was found that a downwind diffuser increases the VAWT performance remarkably. The diffuseraugmented VAWT produced an increment in the maximum coefficient of power of 31.42% at the TSR 0.65 to 0.75. Moreover, the diffuser induced a better self-start ability on the VAWT. The simulation showed that the flow field at the diffuser promotes a flow expansion which created a lower-pressure region at downstream that accelerates the wind toward the VAWT, hence increasing the turbine performance significantly.

Small wind turbines and their potential for internet of things applications

“…Airflow-enhancing devices can boost the power of Darrieus rotors by improving incoming airflow quality. Several enhancements have been explored, including plate deflectors, 144 , 145 rhombus deflectors, 146 wind lenses, 147 , 148 air ducts, 149 and diffusers 150 ( Figure 7 C). While horizontal rotors generally rely on a single form of ducted diffusers, enhancement devices for vertical axis turbines vary in structure.…”

Improvement Performance Twisted Savonius Wind Turbine on Hybrid System: Effect of Flat Plate Deflector Installation

“…Some can be classified into augmented devices in the form of a uni-directional inlet flow and omnidirectional inlet flow, innovative design, blade modification, and building integrated wind turbines (BIWT) [10]. Augmented devices such as deflectors can increase the power coefficient of wind turbines above the Betz limit [11][12][13]. In this case, a flat plate is one deflector type with the most basic shape.…”