Dynamical Analysis On Rub Impact Of Dual-rotor System In Aero-engine,Its Optimization And Rotor Synchronization

To build a more accurate dynamical model of the dual-rotor system,the casing,inner rotor,outer rotor and elastic supports of the elastic support-dual rotor system were modeled as elements and nodes.Then the finite element dynamic equations involving rub impact were derived.For the two cases of co-rotating and counter-rotating respectively,if sudden unbalance occurs,the resulting rub impact force and nonlinear dynamic response of the inner and outer rotors were studied.Subsequently,to be more accurate,the ball bearing was introduced to replace the elastic spring,and a ball-bearing dual-rotor model was established.The rub impact force and nonlinear dynamic response of the system were analyzed,studying the influences of rub impact parameters on the nonlinear response.Furthermore,the multi-objective optimization of the dual-rotor system was performed,and following the idea a practical power turbine rotor was optimized.Finally,the synchronization and anticipating synchronization and their application in rotor measurement were explored.The main research works and the achievements are as follows:1)The dynamical model of the elastic support-dual rotor system was established,and its finite element equation involving rub impact force was deduced and solved,and the variation characteristics of the rub impact force and the response was also obtained.For two rotating cases,i.e.,co-rotating and counter-rotating cases,the influence of sudden unbalance on rub impact force between the rotor and casing was studied,and the resulting dynamic response was analyzed.The influences of sudden unbalance,rubbing stiffness,rubbing clearance and friction coefficient on dynamic response of the dual rotor-casing system were studied.A lot of nonlinear phenomena were observed in the responses.2)The dynamic model of the ball bearing-dual rotor system involving sudden unbalance and rub impact force was established,and its finite element equation was deduced and solved,and the variation characteristics of the rub impact force and the response was also obtained.In the cases of co-rotating and counter-rotating,the influences of the rub impact force between rotor and casing,sudden unbalance,rubbing stiffness,friction clearance and friction coefficient on dynamic response of the bearing-casing-dual rotor were studied.3)For a class of nonlinear dynamical systems,a synchronization scenario through function coupling was presented.The necessary condition for coupling function was given by theoretical analysis,and the theoretical results were verified by simulation.The anticipating synchronization of a class of nonlinear dynamical system was studied.The control method for anticipating synchronization was proposed,and a multistage derived system was established so as to achieve a long anticipating time for chaotic responses of the original system.According to the characteristics of rotor system,by introducing some support measuring signals to the derived system,the derived system could be controlled to fully synchronize with the original rotor system.The result showed that the synchronization was very stable,even for the different initial conditions,the random disturbance and the loosening fault of supporting bolt.The response of the derived system could be used to obtain that of the actual rotor,even in the cases of base disturbance and loosening of bolt.In addition,the variation of rotation angle of the rotor disk,which is hard to be measured in practice,could be obtained by the corresponding variable of the derived system as well.This method provides a new way for acquiring the responses of actual rotor systems.4)The multi-objective dynamic optimization of co-rotating and counter rotating dual rotor systems were carried out,in which the support stiffness was set as the optimization variable and the minimum amplitudes at the disks were desired.For the co-rotating and counter rotating dual rotor systems,the optimization could decrease the amplitudes at the two inner disks by more than 35%,and the amplitudes at the two outer disks by more than 17%.For the turbine rotor in a turbo-shaft,the finite element model was established and the multi-objective dynamic optimization design was carried out.The responses in three points of the shaft and the turbine disk,and the maximum stress in the shaft were taken as the objectives.The stiffness of three elastic supports was chosen as the variables and the critical speed as the constraint.The optimization results could decrease the amplitudes and the stress significantly.