A Numerical Study of Thickness Effect of the Symmetric NACA 4-Digit Airfoils on Self Starting Capability of a 1kW H-Type Vertical Axis Wind Turbine

Abstract

The effect of thickness of the symmetric NACA 4-digit airfoil series on self starting of a 1kW three blades H-type vertical axis wind turbine (VAWT) using computational fluid dynamic (CFD) analysis is the main objective of this study. A sliding interface technique was used to investigate two dimensional unsteady flow around VAWT model by solving the Reynolds Average Navier-Strokes equation with k-e Realizable turbulent model. A novel CFD-dynamic coupling model is proposed to solve the dynamic of VAWT. In this model, while the aerodynamic force acting on the VAWT blades is solved by CFD, the torque of the generator and the dynamic friction force at the bearing applying on the axis of VAWT are modelled vie their physical characteristics. The during time to rotate an angle of 120° of VAWT is one of the principle parameters to investigate the self starting capability. The effect of the starting azimuth angle of blade, the wind velocity and the geometry of the airfoil (NACA 0012, 0015, 0018, 0021) on self starting capability are analysed. The qualitative result show that the considered VAWT has the highest self starting capability when the starting azimuth angle of blade is in the range of [90°÷100°] and it has the lowest self starting capability when the starting azimuth angle is in the range of [45°÷60°]. By using the CFD-dynamic coupling model and by comparing the aerodynamic moment of the wind on the steady three blades to the static friction moment, the considered VAWT rotate at the starting wind velocity of 4 m/s, 3.5 m/s, 3m/s and 3 m/s for NACA 0012, 0015, 0018 and 0021 respectively. The VAWT has the lowest self starting capability with the configuration of NACA 0012 and has the highest capability with NACA 0021.