Research On Vibration Localization And Vibration Reduction Optimization Of Mistuned Bladed Disk In Aero-Engine

Aero-engine are highly complex thermal power machines operating under the conditions of gas compression,expansion,high speed flow and high speed rotor rotating.Aero-engine work in the complex working environment for a long time,the structural strength and reliability determine the aeroengine performance,as the aircraft or other aircraft of the heart,its technical level is seriously restricting the development of China’s aviation industry.The bladed disk system should be circle symmetric structure in theory,but due to the manufacture,installation,wear,in order to suppress the flutter of and other reasons,resulting in the bladed mass,stiffness and natural frequency,this is the mistuning.The mistuning results in the vibration energy of the bladed disk system concentrated on a few blades,causing severe localized phenomena,lead to fatigue failure,the service life of the compressor bladed disk system is also affected.It is very important to study the vibration reduction optimization for reducing the localization of blade amplitude.Therefore,it is important to improve the reliability of aero-engine by studying the vibration localization characteristics and vibration reduction optimization of an aero-engine rotor system.In this paper,the rotor disk system of aero-engine compressor is studied,Firstly,the lumped parameter model of the bladed disk system includes tenon and mortise dry friction and gap is established,the nonlinear dynamic vibration characteristics of the bladed disk system are obtained by numerical simulation.Secondly,on the basis of the fixed interface modal synthesis method,The improving fixed interface prestress modal synthesis method is put forward,the finite element reduction model of bladed disk system is established.Thirdly,based on the improved fixed interface prestress modal synthesis method,the finite element reduction model considering nonlinear contact is established.The effects of the order of excitation,frequency veering,blade and disk stiffness ratio on the vibration localization of the bladed disk system are considered.Fourth,the influence of blade mean frequency on the vibration localization of bladed disk system is analyzed,the vibration frequency distribution characteristics of a detuned bladed disk system are obtained,by analyzing the maximum amplitude of the bladed disk system,the frequency distribution of the blade near the blade is analyzed.Finally,according to the vibration frequency distribution characteristics of the mistuned bladed disk system,based on the finite reduced model of mistuned bladed disk system,the optimal vibration reduction algorithm for vibration reduction of bladed disks is established.Specifically,the work done in this paper is as follows:(1)Based on the tenon and mortise lumped parameter model of bladed disk system,considering the gap and friction state,carried out the research on nonlinear vibration characteristics of bladed disk system,the tenon and mortise gap and dry friction for mistuned bladed disk vibration characteristics are obtained.The results show that the above parameters can not be ignored when analyzing the dynamics of bladed disk system.(2)For the whole bladed disk system,the finite element model is large in number of nodes and elements,If consider the tenon and mortise nonlinear contact and mistuning make this problem difficult to calculate.On the basis of the fixed interface modal synthesis method,The improving fixed interface prestress modal synthesis method is put forward,the finite element reduction model of bladed disk system is established.The modal truncation,and Coriolis force for prestressed effect of vibration characteristics of bladed disk system are discussed.By calculating the eigenvalues of different mode truncation numbers,the results are compared with those of the whole bladed disk,the accuracy of the finite element reduction model is verified.The optimal mode truncation number is obtained in terms of computational accuracy and computer.(3)Based on the improved fixed interface prestress modal synthesis method,the finite element reduction model considering nonlinear contact is established.The effects of the order of excitation,frequency veering,blade and disk stiffness ratio on the vibration localization of the bladed disk system are considered.Firstly,the mistuning parameter identification method under random mistuning and deterministic mistuning is studied,for random mistuning,the Weibull distribution is combined with Monte Carlo simulation technique to identify the mistuning parameters,for deterministic mistuning,a method based on blade static frequency,dichotomy and finite element analysis is adopted.Secondly,in order to evaluate the mistuned bladed disk system localization degree under different excitation order,defines the relative localization factor,discussed the different excitation order and mistuning standard deviation under the influence of the localization characteristics of bladed disk system.Thirdly,analysis of the bladed disk system mode conversion characteristics,in order to evaluate the influence of blade on the vibration localization of the bladed disk system in the frequency steering region,the contribution factor is defined from the angle of modal strain energy.The relations among frequency steering gap,blade contribution factor and localization factor are discussed.Finally,the fixed stiffness of the blade and the fixed stiffness of the wheel are taken into account,the influence of blade and disk stiffness ratio on the vibration characteristics of the bladed disk system is analyzed.(4)Fourth,the influence of blade mean frequency on the vibration localization of bladed disk system is analyzed,the vibration frequency distribution characteristics of a detuned bladed disk system are obtained,by analyzing the maximum amplitude of the bladed disk system,the frequency distribution of the blade near the blade is analyzed.(5)Finally,according to the vibration frequency distribution characteristics of the mistuned bladed disk system,based on the finite reduced model of mistuned bladed disk system,the optimal vibration reduction algorithm for vibration reduction of bladed disks is established.Aiming at the optimization of blade stiffness mismatching arrangement,based on the reduction model of finite element method,vibration reduction optimization is carried out by means of the maximum and minimum values of blade position interchange,on the premise that the calculation accuracy is guaranteed,saving a large number time of calculation,the calculation efficiency is higher.Arrangement optimization of bladed disk system with imbalance of blade mass,Based on the discrete particle swarm optimization algorithm,in order to avoid falling into local optima,introducing mutation operator of genetic algorithm,modelling the genetic particle swarm optimization algorithm.The algorithm inherits the advantages of particle swarm optimization algorithm,such as simple rule,easy to implement and fast convergence,and can avoid falling into local optimum.In view of the blade mass mistuning,the stiffness mistuning arrangement is optimized,firstly,the genetic particle swarm optimization algorithm is used to optimize the arrangement of the mass lost harmonic blades,the obtained arrangement optimization scheme is divided into six isolation zones,in each isolation zone,the installation position of the blade with stiffness detuning is optimized,Finally,the optimization scheme of the arrangement of the bladed disk system satisfying the minimum balance moment and the minimum vibration amplitude of the bladed disk system is obtained.