Abstract
The aerodynamic performance of the blade determines the power and load characteristics of a wind turbine. In this paper, numerical research of the active deformation of an airfoil with equal thickness camber line was carried out, which shows the great potential of this active flow control method to improve the flow field. The NACA0012 is taken as the reference airfoil, and the inflow wind speed is 9 m/s, the chord length of the airfoil is 0.4 m, and the Reynolds number is 2.5 × 105. The influence factors, such as deformation amplitude and deformation frequency on the aerodynamic performance, were studied at different attack angles before and after stall. Studies have shown that: firstly, at different angles of attack, different deformation amplitudes and frequencies have great influence on the aerodynamic performance of the active deformed airfoil. The active deformation can improve the aerodynamic performance of the airfoil in different degrees in deep stall and light stall regions. Secondly, a suitable deformation amplitude and deformation frequency can improve the aerodynamic performance of airfoil stably and effectively in light stall, which occurs when the deformation amplitude equals to 0.02c and the deformation frequency is lower than 2 Hz, and the maximum lift-drag ratio can be increased by about 25%. Before stall, when the deformation frequency is 2 Hz and amplitude is 0.10c, the airfoil will have a negative drag coefficient in the process of deformation, and the airfoil will produce a thrust which is similar to the energy capture of the flapping foil. This is an unexpected discovery in our research.
Highlights
The research of the vertical axis wind turbine started late
Models the airfoiland is atTurbulence a high angle of attack, the flow field is considered to be unsteady, and the fluid can be considered incompressible as attack, the incoming
Because the airfoil is at a high angle of the flow fieldnumber is considered to beincompressible unsteady, and equation is used as the governing equation: the fluid can be considered incompressible as the incoming Mach number is low
Summary
The research of the vertical axis wind turbine started late. The energy acquisition mode of vertical axis wind turbine is as follows: under the action of wind, the blade generates aerodynamic force, which forms the torque to the shaft through the connection between the crossbeam and the shaft, making the wind wheel rotate. The blade is the most important part of the straight blade vertical axis wind turbine [2,3,4]. The blade design of horizontal-axis and vertical-axis wind turbines usually refers to the more suitable airfoil profile of the aircraft. In order to improve the aerodynamic performance of the aircraft, the designers realize the efficient, safe and flexible flight of the aircraft by performing various active and Energies 2019, 12, 4106; doi:10.3390/en12214106 www.mdpi.com/journal/energies
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