Vibration Analysis Of The Dual-rotor System For Aeroengine

The dual-rotor system(low-pressure-high-pressure or internal-external rotor system)of an advanced aero-engine is the core component of an aero-engine,which has a complex structure.It works under high speed,high pressure,high load,high temperature,and other harsh conditions,and is prone to various forms of faults,especially the vibration fault.The vibration fault of the rotor system directly affects the service performance and structural safety of the engine.It is an important task and urgent demand to study the vibration characteristics of the aero-engine dual-rotor system,especially the vibration fault.The vibration faults of the aeroengine dual-rotor system have many forms,such as unbalanced fault,rub-impact fault,misalignment fault,etc.,which are complicated in mechanism and behavior and difficult to study theoretically.The existing dynamic models can not accurately analyze the vibration of the aero-engine dual-rotor system.It has important theoretical value and engineering reference significance to study the vibration characteristics and typical vibration faults of the aero-engine dual-rotor system,and deeply analyze the vibration characteristics and influencing factors of dual-rotor system with typical faults.In this paper,the analytical dynamic model and rigid-flexible coupling simulation model of the dual-rotor system are established.A simulation test rig for the dual-rotor systems is developed,which is similar to the structure and dynamics of the aero-engine rotor.The coupling vibration and transmission law of the dual-rotor system are studied by the method of analytical analysis,multi-body dynamic simulation,and experimental testing.The main factors affecting the vibration are analyzed.The main results are as follows.Aiming at the theoretical analysis requirements of dynamics and vibration characteristics of the aero-engine dual-rotor system,considering multiple supports and the coupling of internal and external rotor structures,the energy method is used to establish an analytical dynamic model.The model has four lumped mass discs(low-pressure compressor,low-pressure turbine,high-pressure compressor,and high-pressure turbine)and five fulcrums with different stiffness characteristics,and the low-pressure turbine shaft is considered as a flexible shaft.Based on the analytical model,the inherent characteristics of the dual-rotor system are analyzed and compared with the finite element results and multi-body dynamics simulation results,which verifies the effectiveness and accuracy of the analytical model.The accurate modeling of an aero-engine dual-rotor system is realized,which lays a foundation for the subsequent vibration characteristics analysis of the dual-rotor system.Based on the analytical dynamic model of the dual-rotor system,the coupling and transmission law of the unbalanced vibration of the dual-rotor system between the inner and outer rotors are studied,and the effects of the unbalanced vector and the stiffness of the intermediate bearing on the vibration are analyzed.The results are verified by the multi-body dynamics simulation method.The results show that the vibration amplitude of the dual-rotor system changes linearly with the unbalance.The stiffness of the intermediate bearing directly affects the transmission of unbalanced vibration.The vibration response of the dual-rotor system with multi-disc and multi-plane random unbalance vector distribution is stable and bounded.Aiming at the typical faults of an aero-engine dual-rotor system,the dynamic model of the dual-rotor system considering the misalignment of fulcrum and blade-casing rub-impact faults are established respectively based on the analytical model.The coupling vibration and the transmission law between the inner and outer rotors under misalignment fault and rub-impact fault are studied respectively.The main factors affecting the vibration and the influence of the two faults on the transmission law of the unbalanced vibration between the high and low pressure rotors are analyzed.Finally,the results are verified by the multi-body dynamics method.Based on the dual-rotor system simulation test-bed which is similar to the real engine structure and dynamics,the modal characteristics,vibration response,and typical fault effects of the dual rotor system are tested and studied.The results show that there is a coupling between the rotors,and the vibration amplitude has a linear relationship with the magnitude of unbalance,which is consistent with the results based on the theoretical analysis.The response characteristics of 2Ni in the dual-rotor system caused by the misalignment of the low-pressure turbine rotor rear fulcrum and the complex frequency vibration response behavior of the dualrotor system caused by the rub-impact fault are consistent with the theoretical analysis results.This paper establishes the dynamic model and simulation model of the rigid-flexible coupling dual-rotor system,which considers the high-pressure shaft and the fan shaft as the rigid shaft,and the low-pressure turbine shaft as the flexible shaft.It can simulate the typical faults of the actual aero-engine dual rotor system.The qualitative analysis and simulation of vibration characteristics of an aero-engine dual-rotor system under the action of unbalance vector change,misalignment,and rub-impact fault are realized.The vibration coupling,transmission,and influence factors of the system are obtained.The research methods and typical results of this paper can further enrich the basic theory of dynamics and vibration of the aero-engine rotor system,and provide important support for engineering practice.