【作者】 张义华；

【导师】 李隆键；

【作者基本信息】 重庆大学 ， 热能工程， 2007， 硕士

【摘要】 随着环境问题的日益突出,能源供应的渐趋紧张,可再生能源越来越引起人们的重视。而作为可再生能源形式的风力发电,不但清洁无污染,而且是可再生能源发电技术中最成熟和最具规模开发条件的发电方式之一,已受到世界各国的欢迎和重视。涉及风力发电的问题很多,而风力机的气动问题是诸多问题中最基本的问题。在气动性能的研究中,应用最广泛的是叶素动量理论,但是由于要以一定的假设为基础,在应用中存在着预测不准确的缺点。随着现代计算机技术的发展和三维湍流模拟技术的提高,CFD方法在风力机气动性能研究中的作用越来越明显。基于此,本文选取了具有代表意义的风力机专用S809翼型和PhaseⅥ叶轮,对其稳态绕流流场进行了数值模拟计算。本文首先建立了翼型流动的二维和三维物理、数学模型,对湍流分别采用Spalart-Allmaras湍流模型和k-ωSST湍流模型进行处理,并采用数值分析方法进行了相应的数值模拟计算。计算区域离散采用四边形或六面体单元进行结构化网格划分,壁面处湍流采用增强壁面函数法进行处理。求解过程中对速度和压力耦合采用SIMPLE算法。计算模型的攻角的变化范围为1°至20°,来流的雷诺数和马赫数分别为1×106和0.07333。数值计算结果与来自DTU的实验数据进行了比较,分析了翼型边界层分离流动现象,并得出了在三维模型下采用Spalart-Allmaras湍流模型时翼型失速性能的数值计算结果较为准确。然后在基于叶片的旋转坐标系中建立了叶片旋转状态下流动的三维物理和数学模型,对湍流采用翼型气动性能计算中较准确的Spalart-Allmaras湍流模型进行处理,同样地采用数值分析方法进行了相应的数值模拟求解。在物理模型建立过程中,利用EXCEL软件生成叶片表面的空间坐标点,在Gambit中生成了PhaseⅥ叶片三维几何模型。求解过程中压力项采用在具有较大的压力梯度的旋转流动中处理比较有效的PRESTO(压力交错)格式离散,其它变量采用二阶迎风格式离散,并采用了分步求解法和欠松弛技术以提高解的收敛速度。针对PhaseⅥ叶轮在UAE实验条件下的气动性能进行了模拟计算,分析了轴扭矩、风能利用系数和叶片径向某些截面上叶素法向力系数的分布特点,并与UAE实验值进行了比较,同时也探讨了翼型气动性能的三维旋转效应。并在此基础上研究了叶片桨距角和叶轮旋转速度对叶轮气动性能的影响情况,为进一步的研究奠定一定的基础。更多还原

【Abstract】 At present, the renewable energy attracts people’s more attentions as the environment is becoming worse and supply of energy is getting tenser. As one type of renewable electricity-generation, wind power is not only clean but also more mature in technology and able to be explored in larger scale compared with other types of renewable energy. Therefore, it is being acclaimed and emphasized by most nations. However, There are lots of problems to be solved concerning about wind power, of which aerodynamic performance is the basic one. To study the aerodynamic performance, mostly widely applied is blade element momentum theory, which is based on several hypothesis that lead to imprecisely predicting aerodynamic performance of wind turbine. But now, with the development of modern computer technology and simulation method of 3D turbulence, CFD is playing more significant roles in studying aerodynamic performance. Based on this, the representative wind turbine S809 airfoil and PhaseⅥrotor were selected as the research objects in the paper and the steady flows around them were simulated.Firstly,both 2D and 3D physical, mathematical models of the flows around the airfoil were built, and the turbulence was treated separately by using Spalart-Allmaras model and k-ωSST model. Then the models were solved numerically. The computational domains were discretized by employing structured quadrilateral or hexahedron meshes, and the turbulence near the wall was treated by applying enhanced wall function method. In the process of computation, the coupled computation of pressure and velocity variable was completed with the SIMPLE algorithm. The computed angles of attack ranged from 1°to 20°and Reynold number and Mach number of incoming flow were set to be 1×106 and 0.07333. Computed results are compared with experimental data from DTU, based on which the boundary separated flows were analyzed and the conclusion can be drawn that the computed results form the 3D and Spalart-Allmaras turbulence model were more accurate.Then 3D physical and mathematical models of the flow around rotational blade were built in the rotational coordinate system based on the blade, and turbulence was computed by using Spalart-Allmaras model which had been proved to be more accurate in computing the aerodynamic performance of the airfoil. Likewise, the models were solved numerically. In the process of building physical model, based on limited blade data spatial coordinates were produced in EXCEL which were input to Gambit and 3D geometric model of the PhaseⅥblade was obtained. In the course of computation, the pressure was discretized by employing the PRESTO scheme which was more valid in treating the rotational flow with highly pressure gradient and other variables were discretized with second order upwind scheme. Multi-step solving and sub-relaxation techniques were applied here to benefit the converging of solutionsThe aerodynamic performance of PhaseⅥrotor was simulated numerically under the UAE conditions, based on which the shaft torque, rotor power coefficient and the normal force coefficients at several radial locations were analyzed. Then they were compared with experimental data from UAE. Meanwhile, the 3D rotation effect on aerodynamic performance of the airfoil was discussed as well. Based on the above, the impacts of the pitch angle and rotation speed on the rotor performance were studied which would lay foundations for further research.更多还原