| At present,onshore units are still the main wind turbines in China,while the northwest region with sand-wind environment is the main distribution area of onshore units,which means that wind turbines have a lot of time to be disturbed by the sand-wind environment during operation,resulting in the reduction of aerodynamic performance and erosion,and ultimately leading to a significant reduction in power generation and economic losses.At the same time,a large amount of time is affected by the dynamic stall effect during the actual operation of the horizontal axis wind turbine,so it is necessary to combine the sand-wind environment with the dynamic stall of the horizontal axis wind turbine airfoil.Taking the horizontal axis wind turbine airfoil S809 as the research object,this paper mainly studies the influence of sand-wind environment on the aerodynamic performance and erosion of the airfoil dynamic stall.The main research contents are as follows:(1)The influence of different particle diameters on aerodynamic performance and erosion of airfoil during dynamic stall was studied.It was found that in the elevation stage,the lift coefficient of airfoil will decrease with the decrease of particle diameters and the drag coefficient will increase with the decrease of particle diameters before reaching the peak value.The smaller the particle diameter,the faster the development of vortices above the suction surface of the wing.At the dynamic stall state of 20±10(k=0.078,Re=0.99×10~6),when the particle diameter is greater than or equal to 20μm,the erosion mainly concentrates on the pressure surface,and the erosion quantity increases with the increase of particle diameter.When the particle diameter is 10μm,the erosion area is mainly distributed in the front edge of the pressure surface and the back edge of the suction surface.When the particle diameter is greater than or equal to20μm,the erosion distribution in dynamic stall process is more similar to that in static high angle of attack,but the erosion quantity is generally smaller than that in static high angle of attack at the same time.(2)The influence of different particle concentration on aerodynamic performance and erosion of airfoil dynamic stall was studied.It was found that in the pitching stage,lift coefficient will decrease with the increase of particle concentration and drag coefficient will increase with the increase of particle concentration before reaching peak value.In the downward stage,with the increase of particle concentration,the flow field will begin to re-attach more quickly,which makes the lift coefficient of the airfoil start to rise more quickly.The higher the concentration of particles,the faster the formation and shedding of vortices above the suction surface of the wing.The vorticity distribution at the leading edge of the wing and at some pressure surfaces will be more complex.Increased particle concentration does not significantly change the trajectory of particles colliding with the airfoil during dynamic stall.When the diameter of particles is the same,the change of concentration will not significantly change the distribution of dynamic stall erosion,but the particle concentration is positively correlated with the erosion during dynamic stall.The effects of increasing particle concentration and decreasing particle diameter on aerodynamic loads and flow fields of airfoils during dynamic stall are generally similar.(3)The aerodynamic characteristics of airfoils are significantly different when they are in different dynamic stall states.In this paper,the influence of dynamic stall state on airfoil aerodynamics and erosion is studied by changing the average angle of attack of dynamic stall.It is found that the aerodynamic characteristics of different dynamic stall states of airfoils are similar to those of sand-wind environment,and the greater the average angle of attack of dynamic stall,the greater the impact.When the particle diameter is greater than or equal to 20μm,the erosion distribution of pressure surface under different dynamic stall states is similar.The erosion values of 50μm and100μm show a similar"U"shape distribution,and the erosion value of 20μm decreases with the increase of"S"value.The erosion range of suction front edge of airfoil decreases with the increase of mean attack angle of dynamic stall.When the particle diameter is 10μm,if the particle can be drawn into the suction surface of the airfoil,the amount of erosion at the suction surface is positively correlated with the average angle of attack of dynamic stall,otherwise,there will be no erosion at the suction surface area.(4)The Detached Eddy Simulation is a high-precision numerical simulation method,which is widely used in the numerical simulation of highly unsteady flow field.Based on the Detached Eddy Simulation,this paper studies the characteristics of dynamic stall flow field of airfoil in sand-wind environment,and finds that:Both DES method and URANS method can be used to calculate the dynamic stall of three-dimensional airfoil in the verification condition,and the results of DES method are in good agreement with the experimental values on the whole.The analytical ability of DES method on three-dimensional effects and details of unsteady flow field is much stronger than URANS method.The results of IDDES method show that when the unsteadiness of the flow field is weak,the three-dimensional effect of 50μm particles in the flow field is weak,but when the unsteadiness of the flow field is strong,a small number of 50μm particles are involved in the vortex above the suction surface,and the particles flow in a three-dimensional state.The results of IDDES method show that the addition of 50μm particles accelerates the formation and development rate of vortex on the suction surface of airfoil,which is consistent with the conclusion obtained by URANS method.When the angle of attack is larger,the pressure distribution and vorticity distribution of the flow field under 50μm condition and clean condition have obvious three-dimensional effect. |
PDF Full Text Request