Numerical analysis of the pitch angle effect on the performance improvement and flow characteristics of the 3-PB Darrieus vertical axis wind turbine

Present work aims to enhance the aerodynamic performance of the three-part-blade (3-PB) Vertical Axis Wind Turbine (VAWT) by setting a pitch angle using the solution of Reynolds averaged Navier-Stokes (RANS) equations in two and three dimensions. The 3-PB turbine with zero pitch angle is taken as the reference for comparison at wind speed of 7 m/s and tip speed ratios (TSRs) from 0.44 to 1.77. Having analyzed five pitch angles using 2D simulation, the best pitch angle of -2° is selected for 3D simulations. Flow characteristics and output torque of both 3-PB turbines with 0 and -2° pitch angles are scrutinized in 3D simulation. The blade with -2° pitch angle in the upwind area significantly contributes to the output torque, resulting in performance improvement for most TSRs. The modified turbine demonstrates the most improvement in average of total torque coefficient at TSR = 0.89, by 13.65%, while the maximum reduction in deviation of total torque coefficient from its average is 16.92% at TSR = 1.33. Based on the results, a delay of about 2° in azimuth angle has happened in dynamic stall phenomenon in the 3-PB turbine with -2° pitch angle. More details about flow structure are given in the paper.