NUMERICAL STUDY TO QUANTIFY THE EFFECTS OF STRUTS CENTRAL HUB ON THE PERFORMANCE OF A THREE DIMENSIONAL VERTICAL AXIS WIND TURBINE USING SLIDING MESH

摘要

A computational fluid dynamic (CFD) analysis is carried out to investigate the effects of struts and central hub in 3D on the overall performance prediction of a three dimensional vertical axis wind turbine (VAWT) with three Darrieus H-type blades. The VAWT has the outer diameter of 2.5m and finite unit length height with expected output of 2KVA. This type of small VAWT are expected to perform better on roof tops of the built-up urban area. The analysis is carried out using sliding mesh concept in commercial CFD software 'Ansys Fluent 13'. It is observed that the struts and central hub assembly induce additional drag and generate strong vortices which caused a substantial decrease in the performance parameters of the turbine. The numerical simulation are carried out over a three dimensional VA WT with and without struts and central hub. It is found that both the cases show a similar trend of the torque ripple for any one blade while for the upstream path, on the contrary the blades experience a drop in performance from 220° to 360° due to the struts and central hub assembly. A detailed comparative analysis between both the cases is made over the TSR values range from 1.5 to 4.5. At TSR=1.5, the performance coefficient of the cases with and without struts and central hub are same. However, for the case of struts and central hub, TSR 4 and above show negative values of power coefficients.