Research On Dynamic Modeling Of Rotating Shaft-Blisk-Casing System And Vibration Characteristics

Aero engine is known as the pearl on the crown of modern industry.As the key component of aero engine,the dynamics modeling of shaft-blisk-casing system has always been the focus and difficulty of research.In the previous studies,most of them focused on the simplified structure of the disk and the casing,but did not consider the influence of the flexibility of the disk and the casing on the dynamics of the shaft-blisk-casing system,and did not consider the influence of the coupling effect between components on the whole system.Aiming at these practical problems,this paper takes the rotating shaft-blisk-casing system as the research object,and considers the effects of rotor system flexibility,coupling between multiple components,gyro moment,centrifugal rigidity and rotation softening.Based on the Carrera unified formula,the high-order beam element is used.Based on Taylor polynomial expansion and Lagrange polynomial expansion,the dynamic model of the rotating shaft-blisk system with rubbing fault was proposed.The dynamic characteristics of the rotating shaft-blisk system and the dynamic characteristics of the system caused by blade rubbing were analyzed.The main research contents of this paper are as follows:(1)Considering gyroscopic effect,centrifugal rigidity effect and rotation softening effect,the dynamic equations of rotating parts(such as rotating shaft and disk)based on Taylor polynomials and Lagrange polynomials are established respectively by using high-order beam elements.The inherent characteristics and amplitude-frequency response characteristics of the rotating shaft and disk in the static and rotating states are analyzed,and the results obtained are compared with the simulation results of ANSYS software to verify the effectiveness of the proposed method.(2)Based on Taylor polynomials and Lagrange polynomials expansion,the dynamics model of the rotating shaft-disk system was established,and the dynamics model of the blisk system was established by the Lagrange polynomials expansion method.For shaft-disk system dynamics model,the analysis of different methods on modeling of rotating shaft-disk inherent characteristic of the system,thus proving the correctness of the modeling by using the Lalrange polynomial expansion method.,and analysis the disk position α,aspect ratio β,disk flexibility and rotation speed of shaft-disk inherent characteristic of the system;The effects of truncation error,blade structural parameters and blade mounting Angle on the natural frequency of the blisk system were analyzed by using the common node method.(3)The dynamic model of the rotating shaft-blisk system was established,and the fixed interface method was used to reduce the dimension of the system,and the influence of truncation error on the natural frequency of the shaft-blisk system was analyzed.The finite element model of the casing was established based on the Lagrange polynomial expansion method.The dynamic model of the casing under different boundary conditions(e.g.,one end is fixed,one end is free,and the two ends are elastic)was established.The convergence analysis was carried out to analyze the influence of modal truncation error on the natural frequency of the casing.(4)Considering the influence of casing flexibility and blade-casing friction collision,a dynamic model of shaft-blisk-casing system with rubbing faults was established,and the effects of rotational speed,minimum clearance,casing stiffness and blade number on the response characteristics of rubbing faults were analyzed.The dynamic characteristics of the system when different blades rub are compared and analyzed by using the time domain waveform and trajectory diagram.