A Numerical Study on Effects of Ice Formation on Vertical-axis Wind Turbine Performance and Flow Field at Optimal Tip Speed Ratio

Abstract

Wind turbines can freeze due to exposure to cold air. Ice formation on the rotor blades of a wind turbine reduces their performance. In the present work, the effects of ice formation on rotor blades of straight-blade vertical-axis wind turbines (SBVAWT) with a three-blade rotor and a NACA 0021 airfoil are numerically evaluated under two-dimensional transient settings by solving the continuity, momentum and turbulence equations become in ANSYS FLUENT. Grid and time step independence was investigated. For validation, the numerical model was compared with experimental data. An experimental ice model from the literature was then used to numerically simulate the iced rotor in two-dimensional transition settings. The numerical simulation of the icy rotor was compared with an ice-free rotor. It was found that ice formation on the rotor blades changed the velocity and pressure fields around the rotor blades at angles of 180—360°, changing the streamlines and increasing the vortices. Furthermore, the maximum and minimum reductions in moment coefficient during blade icing occurred at angles of 225—315° and 45—135°, respectively. Due to ice formation on the rotor blades, the power coefficient of the rotor blades at angles 180—360° decreased drastically, and the power coefficient of the iced rotor was smaller than that of an ice-free rotor. It was concluded that ice formation on the blades of the SBVAWT reduced the average power coefficient of the blades and rotor power coefficient by 94.2% and 95%, respectively.

Keywords

• wind turbine
• vertical axis
• straight blade
• increased icing
• performance