Optimization Study Of Aerodynamic Performance For Small-capacity Vertical Axis Wind Turbines

Wind turbines is the device to absorb wind energy, which can be classified into horizontalaxis wind turbines(HAWT)and vertical axis wind turbines(VAWT).HAWT has been adoptedworldwide for its proven technology, while the vertical axis wind turbine is attracting moreand more attention to for its excellence performance. With the development of moderncomputer technology, CFD is playing more significant roles in studying aerodynamicperformance. Based on this method, this thesis selects NACA0022profile used in straightblade vertical axis wind turbines(SB-VAWT) as the primary profile candidate which ispublished in an international literature. Using Fluent software, the k-ω SST turbulence modeland SIMPLE algorithm were chosen, and sliding mesh technique was applied, to study of theeffects of the methods to improve the performance of wind turbines, such as modifying theblade and trailing edge jet in the blade.When the installation angle is0o, we kept airfoil of the blade symmetrical, and modifiedshape in front of maximum thickness of the blade in order to get an optimized airfoil for avertical axis wind turbine. The results show that, when the ratio between semimajor axis andsemiminor axis in front of the blade’s maximum thickness is3:2, the coefficient of power islarger, and the range with better aerodynamic performance widens. When the tip speed ratioequals1.72, the coefficient of power is largest. The largest Cpequals24.8%, which increasesby28%in contrast to baseline case. The mechanism of optimum is that the blade with amodification of airfoil can resist flow separation better at large attack angle.Based on the3:2modified blade when installation angle is0o. We conducted a furtherinvestigation on sensitivity of installation angles for the modified VAWT. We simulatednumerically vertical axis wind turbines to study of the performance of the wind turbine withbaseline blade and modified blade at different installation angles. The result shows that atdifferent installation angles the VAWT with modified blade is less sensitive than the baselineVAWT, and the working range of high efficiency widens. Aiming at the primary wind turbine, we made a1mm wide slot in the tail of blade in orderto get better performance of the wind turbine. The coefficient of power of the VAWT bytrailing edge blowing of the blade is larger, and the range with better aerodynamicperformance widens. When the tip speed ratio equals2.06, the coefficient of power is largest.The largest Cpequals22.4%, which increases by15.5%in contrast to baseline case. Themechanism of optimum is that the passive jet from the slot can alter the coefficient of pressureon the surface of blade at large attack angle.In conclusion, the methods such as modifying the blade and trailing edge jet on the bladeobviously have the application value.