Geometric Modeling And Isogeometric Analysis Of Turbine Blade Structure

Isogeometric analysis(IGA)is a new numerical method which is devoted to integrate CAD and CAE into a unified framework of mathematical expression.Compared with the traditional finite element analysis method,IGA can improve the accuracy and efficiency of structural analysis to some extent.Turbine blade structure is a complex three-dimensional structure with many irregular curves and surfaces.In meantime,it is prone to bending and twisting along the direction of height.Therefore,it is a prerequisite and key for strength analysis to consider these geometric characteristics to build the geometric model of turbine blade.In addition,the working environment of turbine blades is quite harsh,which are usually subjected to large thermal load,aerodynamic load,vibration load and centrifugal load.Therefore,it is imperative to study the mechanical properties of turbine blades under various loads.In IGA,NURBS(non-uniform rational B-spline)is not only the spline function of geometric modeling but also the basis function of analytical model.By making full use of this advantage,the isogeometric analysis of the structural mechanical behavior of turbine blades is not only conducive to highly precise and efficient numerical simulation,but also is the basis for integrated optimal design,which has important academic significance and application value.Based on NURBS elements and aiming at the three-dimensional turbine blade structure,the geometric modeling of blade body is implemented and the IGA of blade structure are realized by MATLAB programming in this thesis.The main contents of this thesis are presented as follows:Firstly,based on the 3D modeling software and combined with the geometric characteristics of the turbine blade structure,the modeling process and method of the blade body structure of bent-torsional turbine blade are described,and the model characteristics and construction methods of the trailing edge structure are introduced in detail.In order to make the subsequent turbine blade structural analysis and optimal design more convenient,the previous method of using data points for direct modeling is abandoned,and the corresponding structural analysis model is constructed based on NURBS,which builds a bridge between geometric modeling and structural analysis.Then,the 3D turbine blade analysis model based on NURBS is constructed,and the IGA formula based on NURBS solid elements is established.The stress and displacement responses of elastic turbine blades under gravity,centrifugal force and aerodynamic loads are calculated and analyzed by MATLAB programming,and the results are compared with those obtained by ABAQUS,a 3D analysis software.The research indicates that the IGA can accurately conduct the mechanical analysis of the three-dimensional solid structure.Moreover,although the number of control points used in isogeometric analysis is far less than the number of nodes of finite elements,the accuracy of IGA is comparative to that of finite element analysis,which demonstrates the advantages of isogeometric analysis.