Study On Dynamic Balance Of Aeroengine Flexible Rotor Based On Transfer Function

It is very important to study rotor dynamics in aero-engine structure design and analysis.The vibration caused by rotor imbalance accounts for a high proportion of the vibration of the whole engine,which will lead to the reduction of the stability of the engine,and cause damage to rotor blades,casing,bearings and other components in serious cases.Most actual engines are unbalanced due to assembly problems,in which the vibration of high pressure compressor and high pressure turbine is small,and the vibration of fan,low pressure compressor and low pressure turbine is large.Therefore,the dynamic balance of low pressure rotor can effectively reduce the vibration of the engine and improve the safety and reliability of the engine.In order to verify the dynamic balancing effects of two high-speed dynamic balancing methods,influence coefficient method and transfer function method,numerical simulation and experiment are used in this paper.Numerical simulation can effectively avoid the calculation error caused by the limitation of experimental equipment,environmental factors,experimenter’s operation,measurement program,etc.The unbalanced vibration of flexible rotor is simulated by ANSYS,and the dynamic balance process of influence coefficient method and transfer function method is simulated.The results show that the numerical simulation of the dynamic balance of the flexible rotor has good calculation accuracy.In order to further verify the accuracy of the dynamic balancing method,several dynamic balancing experiments were carried out on the flexible rotor test bench to simulate the two dynamic balancing methods,and the effects of the number of disks and the distance between disks on the dynamic balance of the flexible rotor were analyzed.The calculated results were consistent with the numerical simulation results.Then the CFM56-7B low-pressure rotor of high-speed flexible rotor engine was selected as the research object for numerical simulation,and the transfer function of the rotor system was obtained through ANSYS harmonic response analysis.The experiment and simulation results show that the transfer function method has a better balance effect than the influence coefficient method,which can effectively reduce the vibration of the unbalanced rotor and avoid the disadvantage of the influence coefficient method,so it has a good application prospect in the maintenance work of aero-engine.Rubbump fault is one of the important faults of aero-engine caused by rotor imbalance.The reason of the fault is the collision friction caused by too small radial clearance and rotor imbalance displacement.This phenomenon is quite common in aero-engine.Based on the analysis of local fan-casing rubbing caused by unbalanced mass and unbalanced force,a proper dynamic balancing method was adopted to solve the problem of rotor-casing rubbing caused by unbalanced phenomenon.The results show that the phenomenon of unbalanced rotor-casing rubbing can be avoided by proper dynamic balancing method.