Analysis Of Coupling And Nonlinear Dynamic Characteristics Of Micro Gas Turbine Bearing-Rotor System

The micro gas turbine (MGT) is a developing power generation system in recent years. With advantage of high reliability, remote-control, self-diagnosis, it is widely given attention to in aerospace and military fields. Our country puts a high premium on the development of MGT and takes it as important projects. Comparing with America and European countries, our country has a large disparity in the fields of research and application of MGT. In this paper, coupling and nonlinear dynamic characteristics of micro gas turbine bearing-rotor system have been studied. It provided theoretic evidence for the structural design of MGT.At first, the structure and working principle of magnetic suspended rotor system and basic principle of the differential drive control system have been explained in the paper. The electric magnetic force of the system is simplified by adopting two dimensions Taylor progression. Then kinetic models of 5-DOF magnetic suspended spindle system were set up.Secondly the coupling force in radial magnetic bearing of magnetic suspended spindle system and the moment coupling between the front and the rear radial magnetic bearings were analyzed. The distribution and variation of coupling forces along magnetic bearing circle were analyzed. The relations between coupling forces and structure parameters were studied. Considering the influence of coupling forces the coupling kinetic models were established. The simplified kinetic model of the rotor and kinetic model under coupling forces were studied. Then the numerical results were given between coupling and uncoupling models.Analytical result indicates that the system is steady. The natural frequencies were bigger when coupling influence was considered. The first two natural frequencies vary a lot, at the same time natural frequencies increase when coupling forces increased. The coupling forces have a bigger effect on the first two natural frequencies than the third natural frequency. At last, nonlinear dynamic characteristics of magnetic suspended bearing-rotor system are analyzed when nonlinear terms of magnetic force were considered. The kinetic model of rigid magnetic suspended bearing-rotor system and state-space equation were established. Then the stability of magnetic suspended bearing-rotor system was studied in numeric analysis approach. Through numerical analysis the wave-shape figures, phase figures and tracks of the crankshaft figures in some parameter regions were yielded. These figures demonstrated the systemic movement state was steady in these parameter regions. At the same time nonlinear influence factors and coupling influence factors were considered synchronously, and then the more exact kinetic model was established.The analysis in the paper indicates that the coupling factors of micro gas turbine magnetic suspended bearing-rotor system have some effects on dynamic characteristics of the system. At the same time, the rotor can keep on rotating steadily with the rotate speed of 60000r/min under definite eccentricity. The study of this paper provides theoretical reference for controlling the movement state of magnetic suspended rotor system.