Investigation on Influence of Blade Tip Pre-bend and Lengthening on Aerodynamic Characteristics of Wind Turbine
Blade lengthening is an effective method to increase the output of wind turbine.When lengthening the blade tip,it is necessary to consider the blade pre-bend.To analyse the influence of lengthening section pre-bend design on the aerodynamic characteristics of large wind turbine,DTU10MW wind turbine was used as model,and CFD numerical simulation method was used to investigate the effects of straight blade tip lengthening and pre-bend blade tip lengthening on the aerodynamic characteristics of wind turbine.The aerodynamic force and flow characteristics of the surrounding flow field at different spanwise sections of the blade lengthening section were analysed.The investigation results indicate that when the projected length of the blade profile is equal,the thrust increase of the two types of lengthening blades is basically same,and the power increase of the pre-bend lengthening blade is about 60％of the straight lengthening blade;The pre-bend angle reduces the negative pressure in the first half of the chord length of the cross-section airfoil suction surface,resulting in a decrease in the pressure difference between the upper and lower airfoil surfaces.The three-dimensional flow at the blade tip increases the friction loss between the blade and surrounding fluid,and pre-bend design further increases the disturbance of the flow direction and radial direction velocity near the blade,resulting in a wider range of three-dimensional effects at the blade tip and decrease in wind energy absorption efficiency.The investigation can provide reference for blade lengthening reconstruction of large wind turbine.
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