Performance evaluation of a downwind diffuser on vertical axis wind turbine. (21st May 2021)

• Record Type: Journal Article
• Authors: Wang, Xiao Hang; Wong, Kok Hoe; Chong, Wen Tong; Ng, Jo Han; Qiu, Cheng Jun; Khor, Chong Shen
• Other Names: Tong Chong Wen guestEditor.; Chen Wei‐Hsin guestEditor.
• Is Part Of: International journal of energy research. Volume 46:Number 1(2022)
• Page Start: 351
• Page End: 369
• Publication Date: 2021-05-21
• Subjects: CFD simulation -- coefficient of power -- diffuser -- experiment -- vertical axis wind turbine; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.6890
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: 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 diffuser‐augmented 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. Abstract : Experiments and simulations have been conducted to evaluate the effects of a downwind diffuser on the performance of a vertical axis wind turbine. An increment of about 26.79% and 31.42% for the maximum coefficient of torque and coefficient of power respectively were obtained in the experiment compared to bare turbine. The downwind diffuser enables the wind flow expands and causes a low pressure downwind region inducing wind accelerates towards the turbine.