Analysis Of Airfoil Aerodynamic Performance And Turbine Characteristics In Sand-Wind Environments

At present,the domestic onshore wind turbines account for a large proportion,mainly distributed in the northwest of China,north China and other Chinese places,but these areas are also areas with more severe sandstorm impact,which means that the wind turbines will always be exposed to dust in the air.The effect of the particles will reduce the energy absorbed by the wind wheel and reduce the aerodynamic performance of the wind wheel,resulting in a significant reduction in power generation.Therefore,it is necessary to study and analyze the aerodynamic performance and operating characteristics of wind turbines in the sand-wind environment.In this paper,based on the SST k-?turbulence model and the discrete phase model(DPM),simulate the gas-solid two-phase of the S809 airfoil,and analyze the effects of different particle properties on the aerodynamic performance of the airfoil.Secondly,with used the modified Blade Element momentum(BEM)method,apply to the aerodynamic design of wind turbines operating under different working conditions,and analyze the influence of sand-wind environment on the aerodynamic performance of wind turbines.Finally,for the straight blades of wind turbines,with different particle diameter and different particle mass concentrations,analyze the influence of sand particles on the boundary layer.The main research contents are as follows:(1)Numerical simulation of gas-solid two-phase flow with different particle diameter.It is found that when the particle diameter ranged from 5?m to 30?m,the lift coefficient of the airfoil decreased and the drag coefficient increased with the increasing of the particle diameter,when the particle diameter ranged from 30?m to100?m,the lift coefficient of the airfoil increased and the drag coefficient decreased with the increasing of the particle diameter.The minimum lift coefficient of the airfoil and the maximum drag coefficient appear in the particle diameter of about 30?m.(2)Numerical simulation of gas-solid two-phase flow with different particle mass concentrations.It was found that when the angle of attack is greater than 7°,the influence of mass concentration on the aerodynamic performance of the airfoil is obvious.With the increase of mass concentration,the lift coefficient is significantly increased and the drag coefficient is significantly decreased.At the same time,when the mass concentration increases from 1.48kg/m~3 to 5.6kg/m~3,the lift coefficient of the airfoil increases by about 0.59%and the drag coefficient decreases by about1.56%;when the mass concentration increases from 1.48kg/m~3 to 9.8kg/m~3,the lift coefficient of the airfoil increases by approximately 1.19%,and the drag coefficient decreases by approximately 3.18%.(3)Numerical simulation of gas-solid two-phase flow with different particle equivalent density.It was found that when the angle of attack is greater than 7°,the equivalent density has a significant influence on the aerodynamic performance of the airfoil.With the increase of the equivalent density,the lift coefficient is significantly increased and the drag coefficient is significantly diseased.At the same time,when the equivalent density increases from 1.25kg/m~3 to 1.3kg/m~3,the lift coefficient of the airfoil increases by about 0.49%and the drag coefficient decreases by about0.99%;the equivalent density increases from 1.3kg/m~3 to 1.4kg/m~3,the lift coefficient of the airfoil increases by approximately 1.38%and the drag coefficient decreases by approximately 2.88%.(4)Modified Blade Element Momentum theory(BEM)is adopted to design wind turbines operating in clean air and sand-wind environment,to ensure lift and drag coefficients of the airfoil,and calculator the chord and pitch in each section of the blade,and then according to the power output control methods to obtain the wind turbine power curve,thrust curve and torque curve.Finally,from the results it is known that the influence of sand-wind environment on wind turbine performance curve.The influence of sand particles on wind turbines is mainly manifested in the following:the rotor radius of the sandy turbine is smaller than that of the clean turbine,the chord of the sandy turbine aerofoil section is slightly larger than that of the clean turbine,and the pitch of the sandy turbine is slightly smaller than that of the clean turbine.At high wind speeds,the power output of the two turbines operating in the sandy environment are consistent with their operating in the clean air due to the same power control method.At low wind speeds,the power of the sandy turbine is greater than that of the clean turbine when they run in the sandy environment and the thrust of the sandy turbine is less than that of the clean turbine when they run in the sandy environment.The larger power output,the greater the benefit of the wind turbine.The less the thrust,the less the fatigue load the turbine will bear.(5)Compared with clean air,the addition of sand particles of different diameters will always reduce the thickness of the airfoil boundary layer.At the same chord position,the thickness of the airfoil boundary layer tends to decrease first and then increase with the increase of particle diameter,and the thickness of the boundary layer reaches the minimum when the particle diameter is 50?m.Compared with clean air,the thickness of the boundary layer of the airfoil will decrease with the addition of sand particles of different mass concentrations.The larger the particle mass concentration,the smaller the boundary layer thickness of the airfoil.Within different ranges of particle mass concentration,the locations where the maximum reduction in the thickness of the boundary layer occurs are also different.