Influence of friction and clearance in auxiliary bearings on chaotic vibration of a coaxial rotor supported by active magnetic bearings

In many cases of rotating systems, like jet engines, coaxial rotor system is used for power transmission between a high/low pressure turbine and a compressor. In this paper, chaos analysis of a magnetically supported coaxial rotor system in auxiliary bearings is presented, which includes gyroscopic moments of disks and geometric coupling of the magnetic actuators. The nonlinear equations of motion are developed using the Lagrange’s equations and solved by the Rung-Kutta method. Then, the effects of friction and clearance in auxiliary bearings on the chaotic vibration of the coaxial rotor-AMB system are investigated by the dynamic trajectories, power spectra, Poincare´ maps, bifurcation diagrams and maximum Lyapunov exponents. The results show that dynamics of the system can be significantly affected by varying these parameters, so that the system responses reveal a rich variety of nonlinear dynamical phenomena including chaos and jump. Also according to the results of analysis, some threshold values can be obtained with regard to the design of appropriate parameters for this system.