Blade Vibration Analysis Of Aero-engine Rotors Under Torsional Vibration Excitation

Compressor blades and turbine blades are one of the most important parts of aeroengine.The working environment of blades is bad.In addition to withstanding centrifugal force,aerodynamic force and thermal stress of high-speed rotation,compressor blades are also subject to mechanical excitation of rotor system,and the coupling vibration between rotor system and blades are easy to occur.In this case,the blades are prone to fatigue damage,which seriously affects the safety of aero-engine.Therefore,it is very important to study the coupling characteristics of rotor motion and blade vibration for blade design and optimization.In this thesis,the vibration characteristics of compressor blades and turbine shrouded blades under the torsional vibration excitation of rotor are studied,and the work is carried out from the angle of analysis,numerical value and experiment,mainly including the following aspects:1.The Euler-Bernoulli rotating thin-walled beam without considering shear effect is used as mechanical model of compressor blade of Aero-engine.Considering the influence of centrifugal force and geometric nonlinearity,the aerodynamic force of blade in supersonic flow is calculated by the first-order piston theory.The singledegree-of-freedom nonlinear dynamic equation of blade bending vibration under the torsional vibration excitation of rotor is established by Hamilton principle and Galerkin discretization.2.The amplitude-frequency response equation of the non-linear dynamic equation is calculated by the multi-scale method.Then the effects of rotor torsion amplitude,aerodynamic force,rotor steady speed and blade shape parameters on blade amplitudefrequency response characteristics are analyzed.The results show that the blade amplitude increases with the increase of inflow velocity and decreases with the increase of rotor steady speed.Using singularity theory,the topological structure of the system's amplitude-frequency curve is analyzed by selecting bifurcation parameters and opening parameters.The results show that the system is divided into six parameter domains,in which the system response will not jump or bifurcate in two parameter domains.Through the periodic displacement excitation generated by the exciter,the vibration law of the blade under the condition of low wind speed is experimentally studied by using laser vibrometer and low-speed recirculating low-turbulence wind tunnel.The correctness of the analytical law is verified by comparing with the previous analytical and numerical law.3.On the basis of considering the impact force of the rotating shrouded blade,the nonlinear dynamic equation of the bending vibration of the rotating shrouded blade under the torsional vibration excitation of rotor is established by using Hamilton principle and Galerkin discretization.The impact characteristics of shrouded blades under two kinds of impact forces are analyzed.The effects of impact clearance,impact stiffness and rotor steady speed on blade vibration characteristics under symmetrical and asymmetrical clearance conditions are studied.The fourth-order Runge-Kutta method is used to analyze the dynamics of the system,and the effects of different collision clearances on the chaotic dynamic response of the system are studied.The analysis shows that the impact between the blade shrouds decreases the amplitude of the blade,but the vibration response of the blade becomes more complex.With the increase of impact stiffness,the amplitude of the blade decreases dramatically but only in a relatively small range;and with the increase of stable speed,the amplitude of the blade with the crown decreases.This research has achieved some conclusive results,which can provide some guidance for the design,optimization and vibration reduction of aero-engine blades.