叶片前缘磨损形貌特征对风力机翼型气动性能的影响

根据实际风电场中风力机叶片前缘磨损在不同阶段的形貌特征,通过对DU 96-W-180风力机翼型前缘进行改型,建立几何模型,结合SST k-ω湍流模型求解RANS方程,分析了翼型的升力、阻力及流场特性,研究了风力机翼型前缘磨损形貌特征对其气动性能的影响。结果表明,前缘磨损特征为砂眼和小坑时,对翼型的升、阻力系数影响较小;而前缘磨损特征为脱层时,对翼型的升阻特性影响显著,尤其随着攻角增加,升力系数大幅减小,阻力系数急剧增大,并且随着磨损的加剧,减小和增加的幅度逐渐增大。前缘磨损加剧了翼型吸力面尾缘附近的流动分离,使分离点前移;砂眼和小坑对气流在翼型前缘的流动影响较小;脱层对翼型前缘附近流动影响很大,导致翼型表面出现台阶流,气流绕过台阶先发生分离,然后再次附着翼型表面流动。

Influence of blade leading edge erosion features on aerodynamic characteristics of wind turbine airfoil

Because wind turbine blades are exposed to complex natural environment for a long time, as time goes on, rain, snow, dust and other particles will gradually erode the surface of blade, then causing the erosion on the blade surface, especially at the leading edge of the blades, which is the area with the most serious wear. With wind turbine running time increasing, under the impact of various complex particles, the erosion process on wind turbine blades typically starts with the formation of small pits at the leading edge, which quickly develop into gouges with larger size and deeper depth, and then the increasing pits and gouges eventually lead to the fact that material of the leading edge falls off largely, forming delamination. In order to simulate the leading edge erosion of wind turbine as accurately as possible, a geometric model which is close to the actual wear profile was established and a mathematical model which is suitable for airfoil calculation was selected. According to the erosion features on leading edge of wind turbine blade operating in actual wind farm, the leading edge of DU96-W-180 airfoil profile was modified to study the effects of aerodynamic characteristics caused by leading edge erosion on wind turbine blades. At the same time, a geometric model was built and numerical simulations were performed to solve the RANS equation based on SSTk-ωturbulence model. Lift force, drag force and flow field characteristics of the erosion airfoil were analyzed. And then the conclusions were drawn. In the situation that leading edge erosion is characterized by pits and gouges, the coefficients of lift and drag have a small change, and as the attack angle increases, the lift coefficient and lift-drag ratio decrease slightly, and the drag coefficient increases slightly. The influence of leading edge delamination is notable, especially under the situation of high attack angle, and the lift coefficient and lift-drag ratio are significantly reduced and the drag coefficient is sharply enlarged with the increase of the attack angle, and this change becomes more notable with the increase of erosion. The leading edge erosion intensifies the flow separation near the trailing edge of the airfoil suction surface, and makes the separation point move forward. The phenomenon of separation is more and more obvious as the degree of wear and tearing is gradually deepening, and the eddy forms after separation gradually becomes larger, resulting in the fact that lift reduces and resistance increases. Pits and gouges have small influence on the flow near the airfoil leading edge. On the contrary, delamination leads to the step-flow around the airfoil surface, and air bypasses the step with separating flow, and then adheres to the airfoil surface again, so the delamination has a significant impact on the flow near the leading edge, which leads to the deterioration of airfoil aerodynamic performance.