| Due to the complex structure and operation conditions of rotating machinery,it is often difficult to achieve the ideal alignment state,coupling and fulcrum misalignment failures frequently,and even lead to other shafting failures,misalignment has become one of the main faults affecting the safe and stable operation of all kinds of rotating machinery.Although scholars have carried out a lot of research based on the misalignment fault,they mostly study the fault characteristics such as 1,2 times frequency and axis locus.However,the characteristics of misalignment fault in practical engineering are often complicated.Some machinery has other frequency components in addition to 1or 2 frequency doubling,and some machinery mainly contains 1 frequency doubling component,which increases the difficulty in analyzing the generation mechanism of misalignment fault characteristics and distinguishing and diagnosing unbalance and misalignment faults.Therefore,this paper,facing the requirements of characteristic analysis and diagnosis of misalignment fault in engineering,studies the appropriate equivalent simulation method of misalignment fault,in-depth analysis of two typical transmission system coupling misalignment fault excitation source and response characteristics,and carries out test verification,which is of great significance for the analysis and diagnosis of misalignment fault in engineering.It mainly includes:(1)An equivalent simulation analysis method for misalignment fault of rotor system based on multi-body contact transient dynamics is proposed.By shifting(deflecting)the drive speed,the nonlinear contact motion between components is simulated to generate misalignment excitation.Based on the kinematic mechanism of the coupling,the mechanical equivalence between the simulation method and the actual rotor system is analyzed.Taking the misalignment of the coupling as an example,the force analysis of the parallel and Angle misalignment subsystem is carried out.Then briefly introduces the transient contact force simulation method of rotor system and the establishment and solution method of dynamic equation.(2)Aiming at the problem that some mechanical misalignment faults are characterized by 1 or 2 times frequency and higher harmonics,a multi-body dynamics model is established to simulate parallel and Angle misalignment faults in a typical motor-pump system,and the higher harmonics and corresponding phase characteristics are obtained.The transient contact force between bolt and half coupling,roller and inner and outer ring and vibration response of the housing were studied.The generation mechanism of high order harmonic characteristics,the phase characteristics of vibration on both sides of the coupling and the variation rule of vibration response characteristics of the housing were obtained.The correctness of the simulation analysis method to simulate the main fault characteristics is verified by the test.(3)Aiming at the problem that the spectrum characteristics of aero-engine misalignment and unbalance faults are similar and difficult to diagnose,a multibody dynamics model is established with a typical low-pressure rotorintermediate casing system as the research object,and parallel,angular and compound misalignment faults are simulated.The transient contact forces between the flexible coupling,the bearing roller and the inner and outer rings,the bearing outer rings and the intermediate casing as well as the vibration response characteristics of the measuring points of the casing were studied.The generation mechanism of misalignment fault characteristics and the variation rules of axial and radial frequency doubling excitation in the transmission process were obtained,and the significant characteristics of 1-3 frequency doubling misalignment in the axial direction and the variation rules of axial and radial vibration responses were obtained.It can provide some reference for the further studies of the aero-engine misalignment fault and the diagnosis of misalignment and unbalance fault. |
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