| In northwest of China,wind resources are especially abundant,but this area is also the area where affected by dusty environment most seriously.Wind turbines operating in this region,will definitely affected by the sandair flow,the effects have two aspects: one is that the particles in the air will change the flow structure around the airfoil,this effect will eventually change the aerodynamic performance of the airfoil;another one is that the particles in the air may collide into the blade surface,then cause the erosion,this effect will also change the aerodynamic performance of the airfoil and reduce the power generation of wind turbine.Therefore,the study concerning the effect of gas-solid flow on the aerodynamic performance of airfoil and the erosion behavior of the wind turbine blade is indispensable.Firstly,in order to capture the detail of the flow structure around the airfoil,a delayed detached eddy simulation(DDES)method,which is a hybrid Reynolds average Navier-Stokes-Large eddy simulation(RANS-LES),and the discrete phase model are used for the simulation of the flow around NERL S809 airfoil in various dusty environment.Secondly,the erosion behavior of the airfoil surface has studied based on the particles Stokes number,which is a dimensionless number,and the effects of the airfoil shapes are concerned.In the end,the erosion behavior of the rotational wind turbine blade has studied,this part is also based on the particles St okes number.(1)Particles with different dimensions will make various effects on the flow structure around the airfoil,but these effects are also affected by the angle of attack.When the angle of attack(AOA)is too small(≤6.1°)or too large(a stall AOA),the effects will be slight,the largest reduce of the lift coefficient is about 4% comparing to the lift coefficient without the effects of particles.When at 8.2° AOA,particles will make a significant influence on the flow structure around the airfoil: the separation point on the suction surface move forward,the spanwise flow appears,the strongest influence appears when the dimeter of particle is 20μm,the lift coefficient reduce about 7.9%.In general,when the dimeter of particle is small,the ef fect of particle will aggravate gradually with the increasing of the dimeter of particles,but there exists a climax(20 μm),after that these effects will degenerate with the increasing of the dimeter of particles.(2)For airfoil,there exists a critical particles Stokes number(CStk)range,once the particles Stokes number(Stk)is larger than this critical range,the airfoil would be eroded,for instance,the CStk range for S809 is 0.0135-0.0151 at 6.1° AOA.And the erosion extent on the pressure surface of the airfoil would be similar if the particles Stokes number take a same value.Furthermore,the erosion extent will aggravate with the increasing of the particles Stokes number.The CStk value is affected by the AOA,the larger the AOA,the larger the critical particles Stokes number.The area on the pressure surface closing to the leading edge is more prone to be eroded,and the curvature of this area makes a great effect on the erosion character of the airfoil,the airfoil is more prone to be eroded when the curvature of this area is larger.(3)Concerning rotational wind turbine blade,the effect of particles Stokes number on the erosion character is more complicated.For blades,the local particles Stokes number of each section increases gradually from the root to the tip,because of the chord length and the local wind speed,and facts proof that erosion always initiates on the tips,this indicates that there also exists a CStk value for the erosion of wind turbine blade,which is the local Stk value of the eroded section where nearest to the root.Results show that,for the 33 k W wind turbine in Lanzhou University of Technology,the CStk value is about 0.018-0.022.When the Stk take a same value,the average erosion rates are similar in different dusty environments,but the erosion area are different.In additional,if the wind speed also take a same value,then the erosion area would be similar. |
