Nonlinear Vibration Analysis Of Dual Rotor System With Inter-Shaft Bearing Considering Inertia Of Rollers

Inter-shaft bearing functions as a crucial part in dual rotor system.It has many nonlinear characteristics such as Hertz contact,clearance,varying compliance.As inter-shaft bearing operates between high pressure rotor and low pressure rotor,it has significant influence on dynamic characteristics of dual rotor system.This dissertation mainly studies the influence on dual rotor system of inter-shaft bearing which considers the effects of roller inertia.The details are as follow:First,we establish two different kinds of roller bearing modeling considering roller inertia: the model of Harsh which considers the motion of every roller,and the model of Liew which simplified the effect of inertia as centrifugal force.By numerical analysis,we choice the model of liew,which can demonstrate most of the nonlinear characteristics of dual rotor system and has higher computation efficiency.Next,we use the dual rotor system model with inter-shaft bearing to study the influence of roller inertia on the instability of system.We found that it has six different unstable regions in bifurcation picture.With the help of HB-AFT method and Floquet theory,we did some analysis on the mechanic of instability.Then we study the orbit of disk center,Poincare section and spectrum of the dual rotor system as it speed up through each unstable region.Finally,we study the influence of design parameters on the unstable region of dual rotor system.The influence of bearing stiffness,bearing clearance,number of rollers and the eccentricity of disk center,disk mass,stiffness of support,dump is considered in detail.We also did analysis on the instability of dual rotor system with its high pressure rotor and low pressure rotor rotate in different direction.It is found that in this situation,the instability of the system can be weaken significantly.