Study The Dynamic Stall Characteristics Of Wind Turbin Airfoil Under Sand-wind Environment

Wind resource is rich in northwestern China,but it often faces with sand-wind weather.As results,wind turbine blades often run in the sand-wind environment will affect the working life of the wind turbine,which affects wind turbine power generating capacity.Airfoil as an important part of wind turbine blade,have important influence on the aerodynamic performance of wind turbine.The dynamic stall phenomenon of airfoil would occur on wind turbine blades due to the effect of wind turbine yaw,wind shear,and so on,to some extent,which could affect the operating performance of the wind turbine and the force situation.Therefore,this article carry out the wind turbine airfoil dynamic s tall characteristics research under sand environment.This research would benefit for improving the airfoil aerodynamic performance under sand-wind environment.It is also a research hot topic at home and abroad.In the end,the NACA 0012 airfoil was used to verify the numerical accuracy of the turbulence model.The dynamic stall characteristics of wind turbine airfoil are studied by the SST k-?turbulence model and the DPM in this research.Due to the complexity of airfoil dynamic stall,the sliding grid technology to realize the pitch oscillation of airfoil,flow control equation theory is based on the incompressible navier-stokes equations,according to the experimental conditions,Ma=0.0732,Re=1×10~6,?=15?10 sin(??t),and k=0.15 are selected under clean air,through the residual independence verification and validation,the time step and turbulence model validation,finally,SST k-?turbulence model,10~-88 residual and1000 time step are used to numerical simulation,puts forward a set of effective and applicable to this article research the grid generation technique and flow field numerical simulation methods.To study the wind turbine airfoil dynamic stall characteristics under wind and sand environment,in view of the low concentrations single particles,studied the airfoil aerodynamic performance?flow structure and movement characteristics of particles in process of movement,the study found that:under clean air,the aerodynamic performance curve of the airfoil fluctuates around a certain value over time,the lift coefficient C_l,moment coefficient C_m and drag coefficient C_d of the airfoil show periodic change.The addition of particles reduces the aerodynamic of performance the airfoil,and the influence is larger at high angle of attack,but smaller at low angle of attack.The shedding of vortex corresponds to the decrease of lift coefficient,the generation and reattachment of the leading edge separation vortex increases the lift coefficient;the addition of particles makes the separation point slightly earlier,after the flow separation,the addition of particles decreased the pressure coefficient on the suction surface of the airfoil.The particles at low concentrations have little effect on the flow field around the airfoil.With the increase of the airfoil angle of attack,the area of particle away from the airfoil suction surface increases gradually,and the unsteady characteristics become more and more obvious.No matter which Angle of attack the airfoil moves to,the erosion is basically distributed near the leading edge of the airfoil,under the condition of dynamic stall,and the erosion position is slightly off,the maximum erosion rate of the airfoil increases with the increase of the angle of attack.For the addition of small concentration of particles with different diameters,the effects of different diameter particles on the dynamic stall characteristics of airfoil are studied,the study found that:the lift coefficient decreases,the drag coefficient increases and the moment coefficient decreases with the addition of particles,but the local area is slightly different.When the airfoil angle of attack increases(the rising edge of the angle of attack),the loss of lift coefficient under wind and sand environment decreases gradually;when the airfoil angle of attack decreases(the falling edge of the angle of attack),there is irregular fluctuation,but the overall rate of change obviously increases relative to the phase of increasing angle of attack significantly,and the maximum loss of the lift coefficient decrease with the increase of the particle diameter;with the increase of particle diameter,the loss of lift coefficient in the increase of angle of attack decreases gradually.When the particle diameter is less than 50?m,the vorticity near the leading edge of airfoil increases with the increase of particle diameter;the particle concentration are mainly distributed on the suction surface of airfoil,showing good followability,the maximum erosion rate of airfoil decreases with the increase of particle diameter;when the particle diameter is greater than or equal to 50?m,the vorticity near the leading edge of the airfoil decreases with the increase of the particle diameter,the particle concentration on the airfoil suction surface decreases with the increase of the particle diameter,the particle concentration of airfoil pressure surface increases with the increase of particle diameter,at the same time,the particles near the airfoil pressure surface have a wider distribution range,while the particle concentration enrichment area of the airfoil suction surface are further away,the rebound distance between particles and airfoil surface increases after collision,the maximum erosion rate of airfoil increases with the increase of particle diameter.The larger the particle diameter,the closer the erosion position are to the leading edge of the airfoil;the erosion of small diameter particles and airfoil surface are more serious.The effects of dynamic stall characteristics of airfoil with different concentration of particles with the same diameter and are studied.It is found that the angle of attack airfoil increasing stage,with the increase of particle concentration,the peak of lift coefficient and stall angle of attack airfoil decrease gradually,and the divergent angle of attack and peak value of drag coefficient also decrease correspondingly.At the stage the airfoil angle of attack decreases,the airflow reattachment process lags behind the clean air reattachment pr ocess,the lift coefficient reattachment stage are more gentle,and the drag coefficient increases in the reattachment process.With the increase of particle concentration,the airfoil separation point occurs in advance,and the greater the concentration,the earlier the separation point,the vorticity around the airfoil increases,the area of low pressure on the upper surface of the airfoil and the area of high pressure on the lower surface of the airfoil gradually increases,when the particle concentration is low,it has little effect on the pressure around the airfoil,and the area of low pressure on the upper surface of the airfoil is small.The erosions of different particle concentrations on airfoil basically distribute near the leading edge,and the maximum erosion rate of airfoil would increase with the increasing of particle concentration.