Vibration Behaviors Of Low Pressure Rotor On Turbofan Engine With Consider The Surface Contact

Advanced turbofan engine low-pressure rotor system generally includes low-pressure fan rotor,gear coupling structure and low-pressure turbine rotor three parts,the gear coupling structure through the gear interface,positioning interface,bolt connection interface to achieve complex power transmission,interfacial contact is a micro-mechanics process that is less sensitive to interface parameters and assembly processes.In this paper,the turbofan engine as the research background,research the vibration behaviors of low pressure rotor on turbofan engine with consider the surface contact,the main contents and conclusions are as follows:(1)According to the Hertz contact,a large number of contact surfaces in the low-pressure rotor system are considered.Considering the continuity of the contact of the rough surface asperity,the microstructural deformation stage is divided into: initial elastic-plastic deformation,medium-term elastic-plastic deformation,late elastic-plastic deformation,a continuous roughened surface elastic-plastic contact model is established,the simulation results show that the proposed model is in good agreement with the classical KE and ZMC model curves,and the trend is consistent and has the advantages of continuous point.(2)As the aero-engine in the contact surface with more bolts,and the bolt preload will significantly affect the contact surface contact stiffness,a typical bolt connection test bed is established,the experimental results show that the first six natural frequencies of the bolted connection structure increase with the increase of the bolting force,based on the thin layer element theory,the change of the preload of the bolt is simulated by changing the elastic modulus of the thin layer element,and get the contact stiffness model,the change of the contact stiffness of the rough surface is estimated by exploring the natural frequency of the bolt structure with the change of the bolt preload.(3)The couplings of low pressure rotor systems--gear coupling connection structure is analyzed,the contact stiffness mechanics model is obtained by using the obtained bolt connection state,The finite element modeling of the complex sleeve connection structure is realized by the method of thin layer element method,which is equivalent to the bolt connection,the meshing and the contact of the positioning surface.On this basis,the finite element simulation of the turbofan engine low pressure rotor system dynamics,The results show that the unbalanced response of the low-pressure rotor system is linear with theunbalance.With the increase of the bolt tightening torque,the first-order critical speed and the unbalanced response are slightly improved.(4)The existing turbofan engine low pressure rotor system simulation test bench to transform,then,carry out natural frequency test,unbalanced response,bolt preload,etc.The results show that the natural frequency and simulation error of the experimental test are6.67%.With the increase of the imbalance mass,the imbalance response increases linearly.With the increase of the bolt preload,the unbalanced response increases nonlinearly,from the qualitative point of view,the simulation and experimental tests show that the vibration response amplitude of the rotor increases with the increase of the bolt torque.From the quantitative point of view,the error mainly comes from the initial imbalance quality is difficult to determine.In summary,the main nut preload torque has a certain influence on the dynamic characteristics of the rotor system with complex tooth connection.In the design of the low pressure rotor system,the main nut preload of the tooth connection structure should be selected reasonably.