Dynamic Analysis and Independent High-Order Nonlinear Dynamics of a Rotor-Bearing-Finger Seal System

Finger seals are widely investigated because of their excellent sealing performance. The finger beam can deform to adapt to the rotor radial vibration when working. The seal is in contact with the rotor surface. Such nonlinear contact forces induce instability and high-order independent nonlinear vibrations, which are harmful to the rotor system. Previous research has usually focused on the finger itself, while the impact of a particular finger end, called the foot, has not drawn much attention. In this paper, a nonlinear finger seal force model considering the interaction between the feet of adjacent laminates is established. It is characterized by coupling rotor displacement and seal deformation and agrees well with the finite element simulation. Based on the Timoshenko beam theory and short bearing assumption, a rotor-bearing-finger seal system is established. The nonlinear dynamic characteristics of the system are analyzed through spectrum cascades, bifurcation diagrams, Poincaré maps, etc. The effects of rotational speed, eccentricity, pressure difference, and the number of seal laminates are studied. The period doubling evolution of the nonlinear vibrations is discussed. High-order independent nonlinear vibrations are discovered, and their detailed nonlinear mechanisms are revealed. This research provides a theoretical basis for the rotor-bearing-finger seal system.