Nonlinear Dynamic Response Analysis of Time-Varying Mass and Rub-Impact Combined Rotor System

Some rotor system’s mass changes constantly during actual production, increasing the nonlinear movement of the whole system. The dynamics model of the rotor system incorporates the time-varying mass, oil-film force, rub-impact force and unbalance force. The system’s motion properties are successfully recognized by building a Poincaré section mapping. This study describes a method for estimating the dynamic rub-impact state in a time domain trajectory. Otherwise, the function is solved by the Runge-Kutta numerical integration method. The vibration characteristics of the time-varying mass rub-impact combing (TVMRI) rotor system with different speeds and time-varying parameters are investigated by a bifurcation diagram, axis orbits, Poincaré map, time domain waveform diagram, spectrum diagram, and three-dimensional waterfall diagram. The results demonstrate that the time-varying mass intensifies the instability of the system. The contact connection between the rotor and stator has three states: no contact, intermittent contact, and complete contact. The time-varying mass causes the P-1 motion to terminate prematurely, while the chaotic region evolves P-3 and P-6 motions and the P-5 motion is replaced by multi-period and quasi-periodic motions. The mass time-varying coefficient ɛ primarily influences the periodicity and motion distribution region of the rotor system. When ɛ changes, the period-doubling motion of the system in the medium speed area changes dramatically. The mass time-varying amplitude coefficient λ primarily impacts the amplitude of the rotor system. When ɛ gradually grows, and so does the amplitude of each frequency component of the system. This phenomenon is particularly visible in the high-speed zone where the system becomes increasingly unstable. Mass eccentricity not only affects the amplitude of the response, but also affects the motion state of the system and the shape of the whirl orbit. The study’s findings provide a theoretical foundation for the dynamics and engineering design of time-varying mass rotor systems.