Vibration Characteristics And Stability Of Dual Rotor System With Fulcrum-misalignment And Crack Faults

The complex structure of aero-engine,bad operating environment and various failure modes have seriously restricted the development of China's aviation industry.In order to increase the rotor-speed and improving the efficiency of the engine,the modern aircraft engine used more suit dual-rotor structure layout,the misalignment and crack are the two common failure forms,qualitative quantitative analysis system in normal or fault conditions of clarification and dynamic response characteristics of fault vibration mechanism,structure of aircraft engine design,fault diagnosis and operation maintenance has important theoretical value and engineering significance.Based on the research for mechanism of simplified model of rotor and close to the actual combination of finite element model of the double rotor,build a high-voltage protection heart and contain different crack rotor model,through to extract the fault characteristic signal and dynamic characteristics of research,finally based on excitation system stability is analyzed.Specific research contents and results are as follows:Based on convert fulcrum misalignment to bending moment,through the decomposition of torque is attached to the different high voltage protection heart problems can be converted to different heart bending moment on the outer rotor,then by solving twodimensional harmonic balance method to solve the response of the high efficiency and its dynamic response analysis.Dual-rotor internal and external rotating shafts of different heart failure to stimulate the main dual frequency;Moreover,with the increase of misalignment values,the movement trajectory of the outer-dial moves and expands,and presents the different changing forms of "8" type,scissors type and so on.This model can reflect the mechanism and influence rule of high-pressure-fulcrum misalignment faults and is applicable to study the mechanism of rotor model with nonlinear force or other faults.In order to solve the problem of rotor shaft crack in high pressure shaft section in rotor system,the finite element model of double rotor with twelve nodes is constructed.Based on the neutral axis method,the variable stiffness matrix of the crack element is derived and embedded into the dual rotor model with different core faults of the high pressure support.The numerical integration method is used to solve the system response and its characteristic analysis.In the rotating speed area corresponding to the ultraharmonic resonance,the double frequency response induced by different cardiac faults at the highpressure support points is coupled,and the peak value of the ultraharmonic resonance can be significantly amplified.In addition,it is found that when the crack reaches a certain depth,the rotor system is unstable at low speed.Containing the crack fault problems of the stability of rotor system,and based on the Floquet theory and eigenvalue analysis method developed numerical direct method,the stability of multi degree of freedom system set is given and the approximate number of time don't get the influence of the stability region boundary,damping is discussed,the influence of asymmetric rotor gyroscope force on the system.