Study On The Influence Of System Parameter On The Random Response Of Rotor System

In modern manufacturing,there are a lot of rotating machinery.Rotor system is one of the most important components in rotating machinery,and the vibration characteristic will affect safety and stability of rotating machinery.Rotor system may produce greater transient displacement response under the influence of stochastic earthquake excitation,and it could pose a major threat to the safe operation of rotating machinery and lead to an accident.Therefore,the study on the dynamic characteristics of rotor system under the affect of random earthquake excitation has important meaning in theoretic and practice application in the fundamental study and engineering application.In the study of rotor system,scholars often regard the casing is undeformed rigid body,but the vibration of the rotator and machine affect each other and result in it certain flexibility.Such treatment is bound to bring about inaccuracy to the calculating result.So,it is required to regard the rotator and casing as together in the research on dynamic characteristic of the rotor system.And take account of the special structure in some rotating mechanical,the effect because of the rack elasticity,the linkup elasticity between the rack and the stator and the gyroscopic which produced by the asymmetry disk should not be ignored.At present,the dynamic characteristic analysis about multi-degree of freedom rotor system under the effect of earthquake excitation,dynamic excitation of bearing and unbalance excitation are seldom.Aiming at rotating machinery,such as dynamo,and according to rotor laboratary bench and practical project in this thesis,a dual-disk rotor model with multi-degree of freedoms was established.Through the pseudo-excitation algorithm and numerical integral,the effect of system parameter on the random response of rotor system under seismic excitation was studied.Main works for this study are as follow:(1)A 3D entity model was established according to actual rotor test-rig,and the first 16 implicit frequency and vibration types were obtained by using ANSYS Workbench modal analysis,and it laided the foundation for analysis on the random response of rotor system.(2)Building a mechanics model with multi-degree of freedom according to the construction of actual rotor system and rotor laboratary bench.The rack was taken to deal with as elastic body,and it considered not only the elastic rack and its flexible coupling with ground,but also two disks working in parallel and gyroscopic effect to the random response of rotor system were taken into account.Meanwhile,the systematic differential equations of motion was established.This model was closer to actual situation and the result obtained was more practical.(3)Considering the multi-degree of freedom rotor system and using the pseudo-excitation method,the power spectral density curve of rotor system under the white-noise stochastic earthquake excitation and bearing rotary stochastic dynamic excitations was obtained.The influence about some system parameter on the random earthquake response of rotor system was investigated,which include the mass ratio,the eccentric ratio,the casing self stiffness,the inter-casing linking stiffness,the bearing stiffness and the cantilever ratio.(4)The difference on the random response of system under filtration-white-noise seismic excitation and white-noise seismic excitation was comparative analysis.The influence of system parameter on the random response of rotor system under filtration-white-noise seismic excitation,dynamic excitation of bearing and unbalance excitation was investigated,which include the eccentric of disk,the out damping of disk and the damping of casing.A theoretical basis was provided by the results for the appropriate selection of system parameter.