Aerodynamic performance improvement of vertical axis wind turbines through novel techniques

PhD ThesisIn order to improve the aerodynamic performance of the vertical axis wind turbines (VAWTs), the presented research seeks to use the novel idea of three different flow control techniques, Gurney flaps (GF), passive micro vortex generators (MVGs) and leading-edge protuberances to extend the operating range and to suppress aerodynamic instabilities for a small-scale H-type VAWT. Two dimensional simulations are used to assess the impact of various GFs on the isolated aerofoil. It is found that the GFs can enhance the aerodynamic performance of the aerofoil by generating more lift and delaying the onset of stall. The benefit of having GF of 1%c and 2%c height is also shown for H-VAWT achieving significant power improvement at low tip speed ratios (TSRs). The main function of the MVGs is to transfer momentum from outside into the inner boundary layer, leading to the suppression of flow separation. In this study, a set of properly designed MVGs is found to increase the lift and reduce the drag of the isolated aerofoil beyond the stall angle. The VAWT with MVGs control shows significant enhancement in power generation at high TSR ranging from 2 to 3.5. The optimum configuration of the MVGs is found to be located at 20% chord length of the blade, having a rectangular shape and a mounting angle of 16◦. Sinusoidal wave protuberances of the leading edge are numerically investigated to obtain the detailed flow fields for analysis and visualization. The results show that leading-edge protuberances with proper design can improve the lift of the blade near the stall angle and the power generation of the VAWT at TSR ranging from 1 to 2.5. The three passive flow controls have been numerically investigated to show their ability to improve the aerodynamic performance of VAWTs and their strong potential for this sector