An Investigation Of Comparison Among The Straight-bladed Vertical Axis Wind Turbines With Flow Control Techniques

With the continuously serious problem of global warming,fossil energy,environment pollution and the strategic security of national energy,the development of the science and technology of new energy is attached importance by many countries.The wind energy is inexhaustible and abundant.Compared with other new energy,the power generation cost of wind energy is the lowest.The wind turbine is a kind of fluid machinery converting the wind energy to power.There are two categories classified by operation principle and structural form: the horizontal axis wind turbine and vertical axis wind turbine.In the development stage of large-scaling design,the highest-commercialized-application horizontal axis wind turbines are confronted with the following technical challenges: fatigue damage,nonlinear deformation of blade,frozen blade and so forth.Due to the inherent structural peculiarity,vertical axis wind turbines can overcome the above problem easily and they own the advantages of low cost,omni direction of wind,low noise,stable operation,suitability of large scale,convenience for installing and fixing,friendliness to ecoenvironment.However,for lack of high aerodynamic performance,the vertical axis wind turbine urgently requires the flow control techniques to improve the flow structure and aerodynamic performance.Therefore,15 kinds of efficient flow control techinques are applied in vertical axis wind turbine and numerically investigated in the same environment condition.The numerical parameters are determined,such as computational methology,turbulenc model,mesh distribution,time step and so on.In addition,the model of resistant torque of the struts is established.After that,the aerodynamic performance and flow structure of vertical axis wind turbine with Gurney flap,dimple Gurney flap,unilateral flow deflecting gap,bilateral flow deflecting gap,non-circular gap,son-mother leading-edge airfoil slat,special leading-edge airfoil slat for vertical axis wind turbine,unsteady continuous jet,steady synthetic jet and unsteady continuous jet are investigated.The constrastive results provide the references for the development of flow control techniques for vertical axis wind turbine.The main work and conclusion are mentioned below:1.The numerical model is established by a three-straight-bladed vertical axis wind turbine(SB-VAWT)based on NACA0021 airfoil.The reliability of this numerical model is demonstrated and the model is optimized to provide an optimal numerical model for the SB-VAWT with flow control techniques.2.In order to investigate the effects of Gurney flap(GF)installed on outward surface,inward surface and bilateral surface,six models of GF are established: outward GF,inward GF,bilateral GF,outward dimple-GF,inward dimple-GF and bilateral dimple-GF.The aerodynamic performance and flow structure of SB-VAWT with different GF are investigated by CFD method.The numerical results provide the reference for SB-VAWT with GF.3.Three models of gap are put forward to offer more kinetic energy for suctionsurface boundary layer of blade,including the bilateral flow deflecting gap,outward flow deflecting gap,inward flow deflecting gap.Four kinds of gap blalde are established including the non-circular gap.The effects of four kinds of gap on aerodynamic performance and flow structure of SB-VAWT are investigated to provide critical reference for optimization design of gap blade.4.According to the design principle of leading-edge slat in Aeronautics and Astronautics,two kinds of leading-edge airfoil slat are put forward and established including son-mother leading-edge airfoil slat,special leading-edge airfoil slat for vertical axis wind turbine(VAWT-LEAS).However,the son-mother leading-edge airfoil slat cannot control the flow direction effectively and thus a VAWT-LEAS with nozzle effect is put forward.Nevertheless,the VAWT-LEAS leads to a poor performance in the downstream area.Therefore,a telescopic VAWT-LEAS is designed and investigated.5.In the light of the trait that the effective angle of attack of SB-VAWT blade intensively varies with the azimuth angle,4 kinds of control strategy are put forward for continuous jet actuators and synthetic jet actuators and the actuators are mounted at the trailing edge.The novel control strategies can preclude the reduction of aerodynamic performance and validly decrease the air and power consumption.The flow control effect of these to actuaros are investigated contrastively and the numerical results provide a significant reference for the vertical axis wind turbine with jet flow control techniques.