Research On The Nonlinear Dynamics Of Rod-Fastened Rotor Bearing System By Numerical Simulation

In recent years,the gas turbine is widely used in the field of energy generation,because of the rod-fastened structure with multi-disk and various existing nonlinear factors,gas turbine rotor may have different dynamic behaviors from Steam turbine rotor.The gas turbine rotor works in high temperature environment,which may cause relaxation phenomenon of the pre-tightened rod bolts and make the rod rotor system have trouble in operation.Due to the limitation of the traditional linear vibration theory in dealing with such nonlinear problems,research on the nonlinear dynamics of rod-fastened rotor has theoretical and practical significance.Considering the contact effect between two disks,this paper builds a dynamic model of rod-fastened rotor and analyze the nonlinear dynamic characteristics of rotor system under different system parameters by using the theory of bifurcation theory to understand the dynamic characteristics of rod-fastened rotor and the influence of the stress relaxation on it.These work is conducive to providing theoretical support of improving the design and manufacture level and ensuring the safety and reliability of operation.The research content and research results of this paper are as follows:In terms of rotor modeling,according to the contact theory,this paper confirmed the relationship between the preload and contact states,and established the nonlinear motion equation of the rotor bearing system considering the contact effect.The time domain response signal was calculated by using the classical Runge-Kutta method.The influences of rotating speed,unbalanced mass eccentricity and contact stiffness on the nonlinear dynamic characteristics of the rod fastened rotor bearing system are discussed respectively.The study results show that:compared with results of the integral rotor system,the nonlinear behavior of the rod-fastened rotor is more abundant with the rotating speed and the unbalanced mass eccentricity increasing.The numerical results with rotating speed increasing reveal periodic,period-doubling,quasi-periodic,period-doubling and chaotic motion etc.The unbalanced mass eccentricity mainly affects the response characteristics in high speed region,and the unbalanced mass eccentricity range that make the system maintain periodic stable movement enlarges along with reducing rotating speed.The higher the contact stiffness between two discs is,the better the repeatability of the system axis orbits and the stability will be.The effect of stress relaxation of the rod bolt on nonlinear dynamic characteristics of the rotor system was studied.The results indicated that the uniform stress relaxation will cause the disorder of rotor system in high speed region,and the system state is gradually transformed into chaotic motion from a stable periodic motion.The uneven relaxation of each rod bolt stress between the rotor disks will lead to uneven distribution of preload and rotor instability,the most obvious change of stability happen in middle and high speed region;The system response in the low speed region is basically unaffected regardless of uniform or non-uniform relaxation of the preload between the rotor disks.