Abstract:
Vertical Axis Wind Turbines (VAWT) play vital role in renewable energy at present. There are two distinct types of VAWT. They are Savonius type VAWT which works on drag force and Darrieus type VAWT which works on lift force. The use of the NACA airfoil has attracted researchers to design wind turbines. This paper focuses on the selection of the best NACA 2412 airfoil orientation, which gives the maximum performance of a Darrius type VAWT by comparing the net moment coefficient acting on the turbine at various angles of attacks. As a prototype, 1.6 m diameter wind turbine with three blades, which has NACA 2412 airfoil cross section was studied. The aim was to design the turbine enabling the Darrius VAWT to operate with its maximum efficiency. For the analysis, number of models with different NACA 2412 airfoil orientations were analysed from oncoming air velocity 1ms-1 to 10 ms-1. Airfoil orientation was changed by 2.5 degree in the range of 0 degree to 30 degrees. Above mentioned parameters were analysed using Computational Fluid Dynamics (CFD) software package and the ultimate design was obtained in accordance with the results. Boundary layer & Rotating region were designed by using Solid Works and saved the designed files as step files. After that, the selected step files imported to ANSYS 14.5 and generated the mesh files. Hereafter, mesh files exported to FLUENT 14.5 for the simulations. Pressure based 2D planar space was used in the analysis and K-epsilon viscos model was studied under transient time base. It was observed that 5-degree angle orientation of the NACA 2412 airfoil blades with reference to the oncoming air flow line, gives the highest net moment coefficient on the turbine with respect to the wind speeds. Net Moment Coefficient is a dimensionless value. So, study about the dimensionless parameters gives us a universal solution. That means the results from this research addresses all scales of Darrieus wind turbines which has NACA 2412 airfoil cross section.
