Performance analysis of different flanged diffuser-augmented wind turbine configurations

Developing new configurations of flanged diffuser-augmented wind turbines is of great importance to reduce the drag force and enhance the output power as much as possible. Thus, six different designs of diffusers categorized into three groups with and without inlet nozzles are presented and investigated in this study. The three groups include a conical part with a flat flange, a conical part with a semicircular flange, and a conical part with a flange of a quarter of a circular flange at the diffusers' outlets. To assess the performance of these six configurations, a comprehensive 2D axisymmetric model is developed using Reynolds-averaged Navier-Stokes equations coupled with the shear-stress transport k-omega turbulence model. The equations are integrated over the domain using ANSYS FLUENT 2020 R2. The model is numerically simulated and validated using experimental and numerical data. The performance parameters of interest were the power coefficient, the normalized ingested air mass flow rate, the diffuser drag force, and the velocity deficit downstream of the diffuser. Results indicated that combining an inlet nozzle with the diffuser increases the extracted power by 100% and decreases the drag force by 20.7%. In addition, the inlet nozzle depletes the recirculation zone at the diffusers' inlet. The compact flange combines the advantage of the small-height flat flange and the semicircular flange which enhances the extracted power and reduces the drag force. The current findings confirm that although an inlet nozzle can have significant effects on the output power, there is still much work needed to enhance the performance of flanged diffuser-augmented wind turbine designs.