Response Of Vibration Localization In Blade-Rotor-Bearing Non-linear System

Periodic structures are widely used in engineering practice, because of their special mechanical properties of frequency passband and frequency forbidden band, etc.. Mistuned structures can make the mechanical properties of the periodic structures change, and also bring about phenomenon of vibration localization.Blade-rotor-bearing system that is widely used in the gas turbine,that has the unique structural features and complex rotor-bearing form. The turbine work repeatedly at high temperature, pressure, and other harsh environment at high speed, its structure will be exposed to various types of complex conditions. So,blades-rotor-Bearing nonlinear systems has long been focus for a long time. According to statistics, the fatigue failure of engine blade is one of the most common type of failure mode. The high cycle fatigue caused by excitation and self-excitation is considered to be one of the main factor of blade fatigue. In addition, maldistribution of vibration energies makes the position of damage varied.This article will focus on blades-rotor-Bearing nonlinear systems and study its vibration characteristics in the field of structural vibration localization comprehensive analysis. The content can be summarized as the following aspects:First of all, this paper made a comprehensive review on the blades-rotor-bearing nonlinear systems vibration related research status domestic and abroad and analyzed the current modelling method of rotating blade and the calculation method of dynamic response. Newmark method has been introduced for solving dynamic equations, and describes the nonlinear finite element theory for solving contact problems.Secondly, the finite element model of mistuned/tuned blades-rotor-bearing system is established, and the static frequency and the critical speed characteristic of this model are analyzed; the law of the natural frequency and the critical speed influenced by the supporting stiffness of each bearing are researched, and the comparative analysis of modal shapes of the dual rotor system with different ways of supporting stiffness of the intermediate bearing is accomplished; what’s more, the correctness of the critical speed calculation has been validated by the amplitude-frequency response method.Thirdly, the dynamic model of the mistuned/tuned blades-rotor-bearing system with unbalance is established, and then the steady state unbalance response is studied to compare with the dynamic response characteristics in rub-impact fault.The dynamic model in rub-impact fault is established, and the dynamics response characteristics are researched when the rubbing fault occurs on the system respectively, and results show strong nonlinear characteristics:combined frequencies and continuous spectrum appear;In addition the lighter instability phenomenon has happened on the rotor without rubbing.Finally, the model of the mistuned/tuned blades-rotor-bearing system with the support of a nonlinear film bearing has been established.This paper studies the dynamic characteristics of the mistuned/tuned blades-rotor-bearing system under the nonlinear oil film,and provide the basis for the design of the mistuned/tuned blades-rotor-bearing system.