Research On Influence Of Particles On Aerodynamic Performance Of Wind Turbine Airfoil Under Sand-wind Environment

The wind turbine in the northwest has long-term operation in the sand-wind environment.The effect of particles on the power output of the wind turbine is not only caused by the wear of the blades,but also the interaction between particles and air which affects the wind energy.Therefore,it is greatly important to study the interaction between particles and the wall,an d between particles and air.Based on the Euler-Lagrangian method,the SST k-? turbulence model and DPM were used to study the wear law and the influence of different diameter particles on the aerodynamic performance through analyzing the motion characteristic in the fluid field of the special airfoil of S809.In addition,the aero dynamic performance of airfoil(leaf)at different azimuth angles and its influence on torque of the wind turbine were studied under the premise of considering the particle gravity.1)In order to ensure the accuracy of the simulation method,the SST k-? turbulence model and the DPM model used in the simulation were verified.For the SST k-? turbulence model,the Cl and Cd of the S809 airfoil were verified under several Reynolds number through changing the closed constant ?*.As the results showed that ?*=0.09 is more suitable when the attack angle is small(about ?<9°),especially under the small Reynolds number and ?*=0.11 is suited to the big attack angle(about ??9°).In addition,the particle loading type and trajectory density of the DPM model have an effect on the Cl and Cd of the airfoil.It is found that the group type and the 250 particle trajectory density would lead to better results.2)The motion characteristics of different diameter particles in the airfoil flow field and the effect on the aerodynamic performance and turbulent kinetic energy of the airfoil under all Reynolds number were studied.As the results showed that particles smaller than 5?m have good following performance and prominent flow characteristic,the interaction between particles and airfoil wall was not affected by Reynolds number basically.Particles with the diameter between 5 and 50 ?m have interaction with the wall and it is affected greatly by the Reynolds number.When particles are bigger than 50?m,they come to directly impact the section near the leading edge on pressure surface and suction surface,and the impact force increases with the increasing Reynolds number and par ticle diameter.The closer to the blade tip,the smaller diameter of the smallest particles and it becomes one of the reason leading to the different wear rate of each leaf.Under all Reynolds number,the 50 ?m particle has greatest influence on the Cl and Cd of airfoil.When the particle diameter is smaller than 50?m,the Cl decreases and the Cd increases with the increasing diameter.When the diameter is bigger than 50?m,the Cl increases and the Cd decreases.Particles with the diameter of 5?m and 50?m can inhibit the development of turbulent kinetic energy at the Reynolds number Re=2×105 and the latter has the strongest inhibition.3)The simulation value of Cl and Cd are in good agreement with the experimental value under the Reynolds number Re=1×106,and it is selected to study the motion characteristics of the different diameter particles and their influence on aerodynamic performance of the airfoil at several attack angles.As the results showed that the separation vortex is small and has no effect on the track of particles with the diameter of 0.5,10,50 and 100?m at the angle of 8.2°.0.5?m particles are affected slightly by the separation vortex under the angle of 12.2° and inhaled by the separation under the angle of 18.1°.When the particle diameter is smaller than 50?m,the larger the angle,the closer particles near the leading edge along the flow direction when they reach their maximum velocity and the larger the value.When the particle diameter is bigger than 50?m,the change of location is the same as particles smaller than 50?m and the value of the maximum velocity at three angles has little difference.At the same angle,the bigger particle diameter,the longer distance between the position and the leading edge,and the maximum velocity decreases.Particles with the 0.5 and 1?m diameter can increase the Cl of airfoil and the former has stronger effect at the angle of 18.1°.4)Considering the gravity of particle,the aerodynamic performance of the airfoil at different azimuth angles and the force change of blades were studied.As the results showed that with the rotation of wind turbine blades,the angle between the sedimentation direction and the motion direction relative airfoil is periodic.Compared with the Cl and Cd of airfoil at the azimuth angle of 0° and 180°,the Cl and Cd at the azimuth of 0°~180° decrease and the decreasing range comes to the biggest at 90° and increase at the azimuth of 180°~360°and the increasing range comes to the biggest at 270°.Based on the change of airfoil aerodynamic performance,the arising pitch moment and yaw moment change periodically and it is the half of the wind turbine rotation period.Moreover,as the difference of two blades ' peripheral force is different at each azimuth and it is periodic,wind rotor appear the phenomenon of fast and slow which increase the instability of power output.