Analysis On Dynamic Characteristics Of Shaft-Bladed Disk System

In the modern industry,steam turbines,generators,and electric motors are typical rotating machines,all of which use the rotor as the main body of work.Early rotating machinery has a lower operating speed and the operating speed is usually lower than the minimum critical speed.Such a rotor can be regarded as a rigid body.As the working efficiency and the thrust-to-weight ratio increase,the rotor develops more and more in the high speed and slender direction.Both the rotor and the blade should be considered as flexible parts.Therefore,when studying the dynamic characteristics of a blade rotor system at high rotational speeds,the interaction between the blade and the rotor system cannot be separated,and a model that accurately describes the influence of the blade on the dynamic characteristics of the rotor should be established.In this paper,the dynamic model of shaft-bladed disk system is established for the single-disk rotor system with blade,and the influence of blade size on critical speed is studied,which provides a theoretical basis for the simplified modeling method of shaftbladed disk system.For the single-disc rotor system with blades,this paper mainly contains the following points:(1)Based on the classical Jeffcott rotor theory model,the interaction between blade and disk during rotor vibration is taken into account.First,the blade is equivalent to a messed point,and the 4 degree of freedom model is established which analyze the influence of blade mass and rotational inertia on the critical speed.Secondly,two degrees of freedom of blade are introduced,a 6 degree of freedom model is established to analyze the influence of angle of blade on the critical speed.(2)Based on the Lagrange energy method,the dynamic model of the shaft-bladed disk coupling system is established.A 4+2n degree of freedom model is established when blade is equivalent to a single pendulum with mess on top.The differential equations are decoupled,and finally the blade 1-section motion equation is obtained,critical speed numerical solution is solved.The efficiency and accuracy of the proposed method are verified by comparison with finite element solution of threedimensional rotor system.(3)The ANSYS finite element analysis platform was used to establish a single-rotor model with different sizes of blades.The effects of length,width,aspect ratio and stiffness ratio of blades on the critical speed were studied,and also the effect of disk location.(4)Based on the finite element simulation results of three-dimensional model and the theoretical model of the rotor system,according to the influence of blade size parameters on the critical speed,different equivalent principles are established to find simplified model.By comparing with the critical speed calculation of 3D model,the efficiency and accuracy of the modeling method are verified,and the conclusion that the less blade simplification method is the best method is obtained.