Reasearch On Vibration Transfer Characteristics Of Aero-engine System

The aero-engine adopts a dual-rotor structure,which has complex structures such as squeeze oil film dampers,rolling supports and pipeline oil circuits,and is also affected by dual-frequency excitation,airflow excitation and thermal effects,which causes the aero-engine complex vibration characteristics and vibration transmission characteristics.Therefore,the study of aero-engine vibration characteristics and vibration transmission characteristics is of great significance to the design,manufacture and vibration control of aero-engines.This paper takes the aero-engine vibration test bench as the research object,uses the finite element method to model the dynamics of the whole machine,and focuses on the influence of the casing on the inherent characteristics of the whole system,the effect of the intermediate bearing on the main resonance characteristics of the whole system,and the vibration transmission law of the whole system.The specific research content is as follows:Firstly,carry out the dynamic modeling and intrinsic characteristics of the aeroengine.Taking the aero engine vibration test bench as the object,the finite element method is used for dynamic modeling,and the casing affecting natural vibration of the whole aero-engine system is analyzed by comparing the critical speed and vibration modes of the whole aero-engine system with the system without considering the casing.The influence of characteristics is analyzed by changing the support stiffness to the critical speed and vibration mode of the whole machine system.The results show that the removal of the casing has little effect on the inherent characteristics of the first three orders of the whole system,and there is a relative error of 14.6% on the fourth critical speed.The sensitivity of the vibration mode of the whole aero-engine system to different supports is different,so when the stiffness of the support is changed,the phenomenon of vibration mode exchange will occur.Then,the effect of shaft bearings clearance on the main resonance characteristics of the aero-engine system is studied.The shaft bearing clearance of the aero engine is considered as a rolling bearing under the Hertz contact theory.The Newmark-?/NewtonRaphson method is used to solve the dynamic equations of the whole aero-engine system to obtain its steady-state vibration response.The effect of the shaft bearing clearance on the main resonance characteristics of the dual rotor and the casing in the aero-engine.The results show that the increase of the bearing clearance of the shaft bearing will cause vibration jump and bistable phenomenon in the whole aero-engine system.When the bearing clearance is large,there will be combined frequency,and the coupling degree of high and low pressure rotor will decrease suddenly.The large decrease causes the resonance peak to disappear.Finally,the vibration transmission law of the whole system is studied.The vibration transmission rate is defined as the ratio of the root mean square value of the acceleration of the point to be measured to the root mean square value of the acceleration of the vibration source point.Apply unbalanced excitation to different parts of the dual rotor as the vibration source,and then gather the vibration response of the whole aero-engine system.From the vibration response,analyze the vibration transmission rate from different vibration sources to the different measurement points of the casing,and find that transmission rate different vibration sources to the different casing measurement is different,and it is related to the vibration mode.Furthermore,the path transmission rate of the system vibration can also be solved.The path transmission rate is defined as the ratio of the element force of the element connected to the point to be measured and the amplitude of the excitation force at the vibration source.By comparing the path transmission rate,each path can be analyzed contribution to measuring point vibration.Find the path transmission rate of each path from the vibration source to each measuring point of the casing,and compare the path transmission rate to find the main transmission path of the system.The research results provide a reference for the aero-engine design and vibration control of the aero-engine vibration.