Nonparametric Dynamics Modeling And Characteristics Research Of Rotor System With Random Uncertainties

The rotor system,one of the core parts of important equipment in national industries,has developed rapidly in the electric power,aviation,petrochemical,machinery and other fields with the development of science and technology.Rotordynamics has gone through nearly a half century of development and gradually formed a relatively complete theoretical system.However,random uncertainties greaterly influencing the steady state operation of rotating machinery,is an important cause of failure or accident.Thus it’s very important and urgentan to carry out the research of rotor system with uncertain factors.This dissertation,in which the research work focused on the topic of dynamical modeling and characteristics analysis of uncertain rotor system,was mainly supported by the High Technology Research and Development Program of China ’Research(No.2008AA04Z410),the National Natural Fund Project(No.11172260).This study carried out the research on nonparametric modeling,dynamic characterisitics and reliability of rotor system with random uncertainties.The nonparametric modeling method for random Jeffcott rotor system is formed,and the approaches for calculating the dynamic coefficients of random uncertain seal rotor system are rederived.A reliability index calculation method is proposed by combining the spectral density analysis and nonparametric approach.The conclutions can reflect the operating characteristics of the uncertain rotor system,which have an immensely guiding role for ensuring stable and reliable operation of rotating equipment and engineering applications.They are summarized as follows:(1)A non-parametric modeling approach for Jeffcott rotor system wtih random uncertainty is proposed and the response is studied.Importance of different parameters is distinguished by sensitivity analysis of the first-order critical speed.Based on the Monte Carlo method,the effects of the dispersion parameters and the external bounded noise excitation on the vibrational characteristics of the system,such as the critical speed and the vibration amplitude,are investigated.The results show that the influence of uncertainties on the stable operation of rotor system,established the basis for study dynamic characteristics of rotor system in variety of working environments.(2)The dynamic coefficient calculation method of seal rotor system with random uncertainties is proposed.The air flow is not assumed to be in ideal state but of many uncertainties,and uncertain orbit of rotor center was obtained by combining periodical elliptical orbit with bounded noise factors.The disturbance clearance function,constant coefficients of each cavity and sealing force on the rotor were re-derived in the uncertain orbit case.And the simulation by software was employed to verify the conclusions of seal rotor.(3)Dynamic response of uncertainty rotor system under different fault is discussed,and a failure recognition and denoising processing method is proposed.Random matrix model of uncertain rotor systems were established by nonparametric method with faults such as misalignment,unbalance,air excitation,rubbing and coupling faults,fault identification can be conducted according to the different role of the uncertain parameters in the response.An improved neighborhood average noise reduction method was proposed to present the response characteristics of rotor system under random excitation.(4)A new reliability computation method based on spectral density analysis and nonparametric technology of uncertain system was proposed.Both parameter and model uncertainties can be taken into consider,and a large number of information needed for determining the PDF is avoided in the process of analysis in this paper.Furthermore,solving tedious and consuming equations is avoided in this method.The short-term predictability was employed to illustrate the influence of uncertainties on operation state.