Rubbing vibration characteristics of double-rotor system under wave load

Structural characteristics of a certain type of gas turbine double rotor and its hull are analyzed. The wave of a regular form is considered, and the wave load is simplified to the form of sinusoidal force. The rubbing force and nonlinear supporting force of the bearing are deduced as per the Hertz contact theory and Coulomb friction law. The mechanical model of the double rotor system under the combined action of the wave load and rotor friction impact is established, which is solved by the fourth-order Runge-Kutta method. The bifurcation diagram, phase diagram, Poincare section diagram, axis trajectory diagrams, effects of rotor eccentricity, and friction coefficient on the nonlinear dynamic characteristics of the system under rub impact fault are studied. The obtained results show that with an increase in eccentricity, the system enters into a chaotic state through the period doubling and paroxysmal bifurcations, and successively experiences nonlinear behaviors such as periodic 2 bifurcation, periodic 4 bifurcation, and quasi periodic and chaos. In the double rotor system, the nonlinear dynamic behavior of the single period and semi Nermark-Sacker bifurcation occurs with increasing friction coefficient. The present findings can provide a theoretical basis for condition monitoring, fault diagnosis, and design optimization of this type of gas turbine double rotor system.