Effect of flanged diffuser divergence angle on wind turbine: A numerical investigation

Abstract

Power augmentation in a small-scale horizontal axis wind turbine, with its rotor encased in a flanged diffuser is explored. The power output of the wind turbine varies with changes in the diffuser design and the resulting back pressure. Reduction in this back pressure also results in early flow separation at the diffuser surface, which hinders turbine performance. The main aim of this study is to numerically investigate the local configuration of the wind turbine location inside the diffuser by varying diffuser angles and wind speeds. Therefore, shroud and flange were modeled and analyzed using the computational fluid dynamic (CFD) analyses and experiments were performed at two wind speeds 6 m/s and 8 m/s with and without the diffuser for model validation. The divergence angle of 4° was found to have no flow separation, thus maximizing flow rate. The proposed design shows wind speed improvement of up to 1.68 times compared to the baseline configuration. The corresponding optimum flange height was found to be 250 mm. However, increasing the divergence angle had a similar output. The dimensionless location of wind turbine was found to be between 0.45 and 0.5 for 2° and 4° divergence angle respectively. Furthermore, the maximum augmentation location varies with wind speed and diffuser’s divergence angle as described by dimensionless location of wind turbine, thus presenting a noteworthy contribution to the horizontal axis wind turbine area with the flanged diffuser.

Optimization Based on Computational Fluid Dynamics and Machine Learning for the Performance of Diffuser-Augmented Wind Turbines with Inlet Shrouds

“…This research employs the CFD software ANSYS Fluent 2023 R2 to study the threedimensional flow and acoustic fields. In this study, the SST k-ω turbulence model is used as a closure for the Reynolds-averaged Navier-Stokes (RANS) equations, for this model accounts for turbulent shear stress transport, exhibits good performance in near-wall boundary layers [35], and is reliable in predicting flow separation under adverse pressure gradients [34]. Thus, it gains a broad consensus as to its suitability for wind turbine applications [23,[27][28][29][30][31][32][33]35].…”

“…Consideration of the tip clearance in the design of a DAWT is recommended by researchers [32,39], who point out that it is related to the aerodynamic and acoustic characteristics of the DAWTs. Diffuser opening angle was taken as a design parameter in studies performed by researchers [19,30,32,34], who revealed its significant effects on DAWT performance. In the summary of the papers surveyed, some key parameters regarding DAWT design have been collected, such as diffuser flange height/angle, diffuser profile/length/opening angle, rotor axial position, and blade tip clearance.…”

“…Their results affirm that diffusers with a cycloidal profile and small length could perform better while maintaining large flange heights. Jauhar et al [34] numerically performed a parametric study on the effects of diffuser opening angle, flange height, and rotor axial position on a DAWT. They indicated that the power output of the DAWT varies with its diffuser design and the resulting back pressure.…”

“…Applying CFD techniques to analyze the aerodynamics of wind turbines enables a deeper understanding of fluid dynamics within the wind field, thus enabling precise predictions of turbine performance [40,41]. Such a statement is evident from the review of the above papers, and it can be found that most of the above studies were conducted using computational fluid dynamics (CFD), such as Abe and Ohya [19], Abe et al [20], Jafari and Kosasih [22], Roshan et al [23], El-Zahaby et al [24], Heikal et al [27], Klistafani and Mukhsen [28], Anbarsooz et al [29], Arifin et al [30], Ramayee and Supradeepan [32], Hashem et al [33], Jauhar et al [34], Mutasher et al [35], Hashem et al [38], Avallone et al [39], etc. ; and the review paper by Agha et al [42] also emphasized that CFD plays a vital role in the design and performance improvements of the DAWT.…”

Velocity Augmentation Model for an Empty Concentrator-Diffuser-Augmented Wind Turbine and Optimisation of Geometrical Parameters Using Surface Response Methodology

“…Concurrently, the augmentation of velocity for diffusers is significantly influenced by the length of the diffuser and its opening angle [31][32][33][34]. Moreover, adding a flange to the diffuser is thought to further improve velocity augmentation [11,[35][36][37]. While the cylindrical section primarily serves as a housing for the turbine, its throat length is crucial as it can influence airflow, thereby affecting velocity augmentation.…”