Dynamic Analysis Of Gear System In GTF Engine Under Multi Source Excitation

Double helical gear is widely used in high-speed and heavy-duty transmission system because of its high coincidence and strong bearing capacity.In the aero Geared Turbofan(GTF)engine,the double helical star gear system connects fan and low pressure compressor rotor to drive the fan at high speed after reducing speed and increasing torque.Under the conditions of taking off and landing at high angle of attack,the intake distortion caused by the uneven intake of the engine will greatly affect the working state of the engine fan and compressor,with affecting the dynamic performance of the double helical star gear system.Therefore,it has certain theoretical significance and engineering practical value to study the dynamic characteristics of gear system in GTF engine under the coupling effect of internal excitation and external excitation of transient inlet total pressure distortion.This thesis aims at the double helical gear system of the GTF engine,to analyze the dynamic characteristics of the gear system and its influencing factors under multi-source excitation,based on the theory of computational fluid dynamics and the multi-free coupling dynamic model.The main research work of this thesis is as follows:(1)Combined with GTF engine system connection form,the flow field simulation model of fan and compressor rotor is established.Considering the influence factors of steady-state total pressure distortion and transient total pressure distortion,the steady and unsteady simulation calculation is carried out based on NUMECA / fine.The influence law of inlet distortion on the flow field characteristics of fan and compressor is studied.The flow field velocity,entropy,total pressure nephogram and torque fluctuation values under the condition of transient inlet total pressure distortion are obtained.The input and output torque excitation of herringbone star gear system is characterized.The local blockage and boundary layer separation caused by inlet distortion are investigated.Moreover,the influence of distortion parameters on torque fluctuation is analyzed.(2)Based on the potential energy method,the time-varying meshing stiffness of the gear is calculated by using slicing method,taking into account the end face deformation,axial deformation and tooth matrix deformation of double helical gear.Based on the error equivalent model,the eccentricity error,installation error and tooth profile error of the transmission system are equivalent to the meshing line direction.The static transmission error of gear is calculated.(3)Considering the internal and external excitation factors such as tooth meshing stiffness,transmission error,backlash,meshing damping and transient inlet total pressure distortion,the bending torsion shaft coupling dynamic model of double helical star gear system under multi-source excitation is established,based on lumped parameter method.The vibration response and dynamic engagement force of gear system under multi-source excitation are obtained by longgekutta method.In addition,the load sharing characteristics of gear system are analyzed.(4)Coupling dynamic model based on herringbone star gear system,the dynamic response of gear system under different excitation is analyzed by changing the single error variable or total pressure distortion parameter.Furthermore,the sensitivity of gear system vibration response to internal and external excitations such as eccentricity error,installation error and inlet total pressure distortion is studied.The load sharing characteristics of the gear system are evaluated,and the influence of different excitation on the load sharing characteristics of the gear system is analyzed.