Modal Analysis And Design Of Wind Turbine Blades

Wind energy is a clean, non-polluting, renewable and widely used renewable energy source. The use of wind energy is becoming more and more extensive. Over the past 30 years, wind power is one of the fastest developing areas, and the wind power technology has been greatly developed in the field of theoretical research and application. Fan power from the previous hundred watt level gradually developed to the current MW class. With the increasing of power, the traditional design method of the wind turbine cannot fully meet the requirements of the structural stability of large power wind turbine design. Blade is the core component of wind turbine. Blade design directly affects the safe and reliable operation of wind turbines and the output of power stability. Seeking better design method and continuous optimization to design a better performance of wind turbine blades. Wind turbine blade is an elastic structure, the load on the blade has the characteristics of cross- change and random, so the vibration is inevitable. And the problem of vibration is directly related to the stability and reliability of the wind turbine operation. So it is necessary to study the vibration characteristics of the model. To this end, this paper mainly on the 1MW wind turbine blades were designed and the modal analysis of the blade was carried out. The main research contents of this paper are as follows:1. Wind turbine blade designBased on the aerodynamics of wind turbine, some parameters such as the rated power, the rated wind speed and the wind energy utilization coefficient can be calculated, and other parameters such as the diameter of the blade can be calculated. For some gas blade aerodynamic parameters, such as length, torsion angle and other parameters to calculate the used design method. In this paper, the aerodynamic shape parameters are calculated by using the simplified method, the Glauert design method and the Wilson design method. Get the airfoil chord and twist angle, and carries on the comparison. After analysis the results of Wilson is simplified design method and Glauert design method is more accurate.2. Aerodynamic characteristics analysis of blade airfoilGambit software was used to establish the calculation model of the blade airfoil, and the Fluent software was used to calculate the grid division and boundary type. Finally, the surface pressure coefficient distribution, pressure contour and velocity contour of the airfoil at different angles of attack are obtained by using the NACA4412 at certain Reynolds number and rated wind speed.3. Blade 3D modeling and modal analysisBefore the three- dimensional modeling of the blade and need to use special airfoil design software Profili selected wind turbine blade airfoil NACA 4412, according to a chapter of using Wilson method is the calculation of the blade element chord length and twist angle to select the blade element, it is possible to obtain a two-dimensional coordinates of each airfoil, although after coordinate transformation based on point can be calculated each blade element section of three-dimensional coordinates. Finally, the 3D solid modeling of the blade is made by using Solid Works.According to the 3D solid model of wind turbine blade, the blade can be analyzed. The import ANSYS Workbench blade completed three-dimensional model, finite element mesh, then the constraint conditions of the blade set. After solving the obtained modal graph leaves, extract the first six order modal analysis of blade. Draws the conclusion, i.e. blade mode shapes are mainly three: wave vibration, swing and torsional vibration; blade vibration energy is mainly concentrated in the first order and second order vibration mode and vibration is mainly to wave vibration; blade modal shape of the higher order, larger amplitude, the vibration performance of the more complex. Finally, through the frequency analysis, and obtains the resonance will not occur in the running process of the 1MW wind turbine.