Experimental And Simulation Study On Aerodynamic Performance Of Deformable Blade For Vertical Axis Wind Turbine

Severe energy crises and environmental pollution are forcing people to find sustainable alternative energy sources,and wind energy has become the fastest growing clean energy source.The aerodynamic characteristics of vertical axis wind turbine blades are complex.How to use effective flow control method to suppress blade flow separation plays an important role in improving the aerodynamic performance of wind turbines.From an aerodynamic point of view,the front and rear edge deflection of the wing has a high aerodynamic efficiency.Therefore,in the research of adaptive wing technology,changing the front and rear edge deflection angle of the wing has always been the focus of researchers in adaptive wing technology.If an adaptive structural system can be used to change the chordwise camber of the wing while maintaining the smoothness of the airfoil and the curvature is continuous,compared with the wings with traditional flaps and auxiliary flaps,the adaptive wings can well inhibit flow separation,and the lift-to-drag ratio can be significantly improved.Therefore,this paper is devoted to the application of this concept to the blades of linear-axis vertical-axis wind turbines.The experimental and simulation methods are used to study the aerodynamic characteristics of the deformed blades under quasi-steady and unsteady conditions.In this paper,a new type of blade model driven by single input for vertical axis wind turbine was developed,and it could achieve synchronous active deformation for both of blade leading edge and trailing edge.Firstly,according to the concept of ribs,NACA0012airfoil was taken as an example.Based on the constant deflection and deformation of the blade leading and trailing edges with constant thickness,the mechanical structure and skin adhesion mechanism with adhesion mechanism of pretension was adopted.In this way,the adaptive blade could achieve reciprocating smooth deformation with different cambers.Secondly,the experimental platform for measure of wind tunnel force and flow visualization was built up,where the smoke wire instrument,seven-hole probe,two-component balance were applied for conducting measurement of quasi steady force and flow visualization under different deformation quantities.Finally,the aerodynamic performance of adaptive blade under different deformation factors was revealed.the experimental results in this paper can provide reference for subsequent unsteady experiments.the numerical simulation research of equal thickness mid-arc active amoeboid movement is carried out for airfoils suitable for vertical axis wind turbines.The NACA0012 is taken as the reference airfoil,and the inflow wind speed is 9m/s,the chord length of the airfoil is 0.4m,and the Reynolds number is 2.5×10~5.The influence factors such as deformation amplitude and deformation frequency on the aerodynamic performance are respectively studied at different attack angles before and after stall.Studies have shown that:At different angles of attack,different deformation amplitudes and frequencies have great influence on the aerodynamic performance of the active deformed airfoil.Appropriate deformation amplitudes and frequencies can stably and effectively improve the aerodynamic performance of the airfoil.At a certain deformation frequency and amplitude,the airfoil will have negative or infinitely close to zero drag coefficient during its deformation.At this time,the lift-to-drag ratio will be greatly increased,the airfoil will generate thrust,and the aerodynamic performance of the airfoil will be greatly improved.Finally,in the experiment of unsteady aerodynamic characteristics of deformed blades,the deformation of the blade is realized by the characteristic curve of the trigonometric function of the stepper motor control system.The unsteady aerodynamic force under different deformation frequencies and different deformation amplitudes of the blade under fixed angle of attack is studied.The law of dynamics is compared with the aerodynamic force of rigid blades at the same angle of attack,explaining the cause of aerodynamic changes from the flow field.In the experiment of blade pitch synchronous deformation motion,the pitch synchronous deformation motion is realized by the blade self-deformation motion combined with the synchronous rotation motion of the rotating platform,and compared with the rigid blade to explore how the blade can improve the aerodynamic characteristics through deformation in the pitching motion.