Nonlinear dynamics analysis of rotor-brush seal system

Abstract

When a gas turbine is working under high temperature, high pressure, and high velocity conditions, complex dynamic behavior and faults arise. These can seriously affect the security and reliability of the system, so it is important to further study nonlinear dynamic characteristics of the rotor-seal system. The seal force model of a brush seal was proposed, considering the interactions among bristle pack, flow force, and rotor, and a nonlinear dynamic model of the rotor-seal system was established. The influences of different geometries and operation parameters, such as rotor speed, installation spacing, damping, and rotor mass on the nonlinear characteristics of the system were discussed. The bifurcation scenario, vibration response, and stability of the rotor-seal system were analyzed by bifurcation diagram, time history, axis orbit, phase portrait, phase trajectory, Poincaré map, and frequency spectrum. The results showed that with a seal force the critical speed was greater than that without seal force conditions. The vibration amplitude of the rotor decreased with increase of damping and installation spacing. When the mass of the rotor increased, the vibration amplitude decreased significantly, which added stability to the rotor.