基于Stokes数的风力机叶片风沙冲蚀磨损研究

The main distribution regions of onshore wind power in China, as Xinjiang, Gansu,etc., often suffer from severe sandy and dusty weather. So erosion on wind turbine blades is inevitable, which will seriously affect the aerodynamic characteristics and life of wind turbine. The results show that the erosion mainly occurs on the leading edge of wind turbine blade. Leading edge erosion can cause the airfoil drag force increases 80%-500% and the lift force decreases 40%, so as the great loss of annual generating capacity of wind turbine, which is up to 25%. The present studies on wind turbine blade erosion mainly aim at the blade material erosion characteristics caused by sand and dust particles. However, the mathematical model and numerical prediction method of blade erosion are lacking..According to the wind-blown sand distribution characteristics in Hexi area of Gansu Province, the mechanism of wind turbine blade coating erosion in the wind-sand environment will be revealed by the method of wind-blown sand erosion experiments. And the mathematical expressions will be obtained between the blade coating material erosion rate and the particle impact velocity, particle impact angle and particle diameter. According to the relation between the blade coating material erosion rate and the particle impact velocity and particle diameter, combining with the expression between the blade coating material erosion rate and particle impact angle, the mathematical model between the blade coating material erosion rate and the Stokes number will be obtained. Combining this model with the models of gas-solid two-phase flow based on N-S equations, a numerical prediction method of wind-blown sand erosion of wind turbine blade will be proposed.

我国陆上风电的主要分布地区（新疆、甘肃等）常面临风沙天气，沙尘对风力机叶片的磨损严重影响其性能和寿命，研究表明，磨损主要发生在叶片前缘，前缘少量磨损将引起翼型80%-500%的阻力增加和40%的升力减小，导致机组年发电量损失高达25%。目前，风沙对风力机叶片的磨损研究主要围绕沙尘对叶片材料的磨损特性，缺乏适用的磨损模型及预测方法。.本项目根据甘肃河西地区的风沙特性参数，开展风力机叶片涂层材料的风沙冲蚀磨损实验，研究其风沙磨损特性；基于实验数据，分别得到叶片涂层材料磨损率与颗粒直径、冲击速度和冲击角的关系式；并由Stokes数与颗粒冲击速度和直径的关系，得到叶片涂层材料磨损率与Stokes数的关系式，进而结合颗粒冲击角与叶片涂层材料磨损率的关系，建立基于Stokes数的风力机叶片风沙冲蚀磨损数学模型；基于N-S方程，结合该磨损模型和气固两相流模型，提出一种风沙对风力机叶片磨损的数值预测方法。

我国陆上风电的主要分布地区（新疆、甘肃等）常面临风沙天气，沙尘对风力机叶片的磨损严重影响其性能和寿命，风沙对风力机叶片的磨损研究缺乏针对性的磨损机理分析和磨损模型及数值预测方法。依托风沙风洞开展了叶片涂层材料平板试样的冲蚀磨损实验，通过研究沙尘的粒径、浓度、冲击角和冲击速度对叶片涂层冲蚀磨损的规律，沙尘与叶片碰撞过程中颗粒运动和反弹轨迹，风沙流对叶片涂层冲蚀磨损的形式、表面形貌和粗糙度变化规律，分析了叶片涂层材料的风沙冲蚀磨损机理。研究发现，叶片涂层表现出典型的塑性材料磨损特性，总磨损量由切削磨损量与冲击磨损量组成，切削磨损量随冲击角增大为先增后降，在30°附近达最大值，冲击磨损量则持续增大，在90°时达最大值；小冲击角时，切削作用占主导，主要形成“海浪状”与“耕犁状”脱层，大冲击角时，正向应力占主导，主要形成“海浪状”磨损形貌。磨损量随冲击角度增大先增后减，最大磨损量在30°左右，最大冲蚀率在20°左右；涂层磨损量随冲击速度的增加而增大；沙尘浓度对冲蚀率影响很小；形状因子小于1的颗粒比球形颗粒对翼型的磨损程度更大。研究得到了沙尘颗粒冲击角、冲击速度和粒径与风力机叶片涂层材料磨损率之间的变化规律；得到了 Stokes 数和叶片涂层磨损率之间的规律，并结合沙尘冲击角对叶片涂层材料磨损率的影响规律，建立了基于 Stokes 数等三种方法的风力机叶片风沙冲蚀磨损数学模型；得到了风沙对风力机叶片冲蚀磨损的临界Stokes数范围。采用欧拉-拉格朗日法求解风沙气固两相流动，离散相采用拉格朗日方法进行描述，并耦合本项目得到的叶片涂层风沙冲蚀磨损数学模型，得到了一种风力机叶片涂层风沙冲蚀磨损率的数值预测方法；进而研究了风力机翼型和叶片的风沙两相流动及冲蚀磨损特性。研究成果为风力机叶片的抗风沙磨损设计提供了理论依据和技术指导，提供了一种叶片的风沙冲蚀磨损预测方法。