Modeling, Nonlinear Dynamics, and Bifurcation Analysis of the Rotor-Seal System Using a Subharmonic Sampling Strategy

Rotors are used to transfer power from one component to the other component in various rotor dynamics applications like steam turbines, aerospace systems, and power generators. In certain applications, the seal is an important and inevitable component of the rotor dynamic system. The linear dynamics of the rotor is converted into nonlinear in the presence of a seal. The presence of a seal, can sometimes, trigger self-excited vibrations in rotor/seal systems. Generally, the amplitude of vibration during such vibrations is several times higher than normal steady-state vibrations. Due to this, other faults like transverse crack initialization and rotor/stator rub get accelerated. The rotating machinery working at high spinning speeds is more prone to this type of instability. Hence, the stability limits of the rotor/seal system must be known in advance for the safe operation of the rotating machinery. The dynamic behavior of such a system qualitatively varies corresponding to different system parameters of the rotating machinery. Cumbersome analytical methods have been used in the past for bifurcation analysis of rotor/seal systems. In the present work, system bifurcations have been investigated using a subharmonic sampling rate strategy. The proposed method is easy to implement and numerically efficient. The effect of various parameters like the spinning speed of the rotor, unstable mass, and seal clearance is investigated for the stability of the rotor/seal system. Experimental testing is done to verify the simulation results.