Whole Vibration Modeling And Nonlinear Dynamic Analysis Of Aero-engine With Structure Clearance

Due to manufacturing and assembly error,abrasion,structure clearance is universally existing in aero-engine rotor-bearing-casing coupling system,which contained the following part: firstly,fit loosening clearance between outer ring and hole of bearing house;secondly,working clearance between internal and external raceway of roller in rolling bearing;thirdly,rubbing clearance between blade and casing.These typical structure clearances will cause strong nonlinear characteristics of connection or bearing stiffness,which will cause the whole vibration showing complex nonlinear vibration laws and characteristics.In order to analyze these fault characteristics effectively and control aero-engine whole vibration purposively,aero-engine whole vibration modeling and nonlinear dynamics have been researched in this paper.The main content is following:(1)A certain type unmanned flight for small engine whole vibration coupled dynamic model is established by using the finite element beam element and nonlinear response is solved by numerical integral algorithm.It can provide coupling dynamic model of the engine for simulating strong nonlinear vibration response problems caused by the structure clearances.(2)The characteristics of the fit looseness fault between the bearing and bearing house are studied.Firstly,Outer ring and bearing house with fit looseness fault model is put forward.The typical connector stiffness nonlinear problem exists in the vibration radial direction in the model.According to stiffness nonlinear problems between two connectors,asynchronous response characteristics of connectors looseness fault are studied.A lumped mass model with connectors looseness fault is established.The response of the system is obtained by numerical integration methods and the asynchronous response characteristics are analyzed.Rig with connectors looseness fault is established and the asynchronous response laws are verified by experiments.Based on the rotor-rolling bearing rig,coupling dynamics model of rotor-bearing rig with bearing outer ring and bearing house fit looseness fault is established.System nonlinear response is obtained by numerical integration algorithm.The influence of tightening torque on bearing response is analyzed.Lastly,the fit looseness fault model is used in a certain type small engine model and casing acceleration characteristics are obtained,which are compared with test data.Simulation and test results show the same fault characteristics.(3)The whole vibration response characteristics of engine are studied considering radial clearance of rolling bearing.For a small engine whole vibration finite element model,rolling bearing radial clearance at different supports are considered and the response sensitivity of the wholemachine vibration is analyzed.For the high sensitivity support,contacting state of the rotor,outer ring of rolling bearing and nonlinear response laws at different rotating speeds are analyzed.The contact force between rolling bearing and rotor,the influence of different radial clearance on the contact force were studied.It reveals the influence of the radial clearance on the stability of the operation of rotor.(4)Blade-casing rubbing fault model and the casing response characteristics under blade-casing rubbing fault are studied.A new model for blade-casing rubbing fault is established.Blades are considered as rectangular beam model,the blade-disc coupling dynamics model and the coordinate transformation between rotor and blade are considered.Rubbing force changing caused by uneven clearance between blades is considered.The new rubbing model is applied to a certain type small engine.The engine whole vibration model with rubbing fault is established.The numerical integral method was applied to obtain the casing acceleration response and blade response laws.Rubbing test on aero-engine rotor rig with casing is conducted.Experiments validated the modeling correctly.Finally,the single-point rubbing model and the local rubbing model are applied to the small engine model.The casing response characteristics are analyzed.