Design, CFD Analysis, and Prototype Testing of Brim Diffuser Shrouded Horizontal Axis Wind Turbine

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Addis Ababa University


In lower wind speed regions, the generation of electrical power from conventional small-scale horizontal axis wind turbines is very difficult due to ineffective power extraction in lower wind speed. However, the introduction of a flanged diffuser that shrouds the wind turbine is used to increase and accelerate the wind speed that approach to wind turbine. This will permit extract efficient power at lower wind speed regions. This research addresses the design, optimization, model 3D Print or manufacturing, and experimental testing of a model diffuser augmented wind turbine. 2D CFD simulations were carried out to examine an optimum geometry of brim diffuser by utilizing different optimization techniques. All samples have the same dimensions in diffuser length, entrance area, exit area, and brim (or flange) length but they vary in sectional shape of diffuser and flange angles. Brim angles of these tested samples vary from 0 20 to 0 20 .The simulation shows that the curve sectional shape of a brimmed diffuser increases the velocity of the approaching wind speed by 7.06 % when compare to straight sectional shape. And also, from different flange angles for the curved sectional shape of brim diffuser, 10 0 flange angle improve the velocity augmentation by 4.07 % when compared to normal flange angel. Besides numerical result shows that the boundary layer flow separation points along inside of a diffuser greatly affect the acceleration of wind flow through a brimmed diffuser. Subsequently, a MATLAB code is developed to optimize the blade twist angle and chord distributions. After this, the performance analysis of the optimized brim diffuser shrouded horizontal axis wind turbine is analyzed by using ANSYS- FLUENT. The CFD result shows that the optimized shrouded wind turbine increases the velocity and power augmentation by a factor of 1.58 and 3.78 respectively when compared to the performance of an unshrouded wind turbine with the same swept area and wind speed. Lastly, the prototype of shrouded turbine is manufactured and test its performance in the wind tunnel in the Addis Ababa Institute of Technology’s laboratory. The experimental result is verified with numerical result with reasonable small deviation which will be suitable for the implementation of a shrouded turbine for lower wind speed regions for rural electrification.



Augmentation, Brim diffuser, CFD, Optimized, Experimental testing, wind turbine