Dynamic Characteristic Research Of Gear Rotor System Considering Nonlinear Meshinig

Gear rotor system is one of the widest movement transmission devices in various sorts of mechanical equipment. With the increased demand for high speed machinery, gear rotor system put a higher requirement, high precision, high speed, and low noise as the direction of development. Its mechanical and working performance is of important influence to the whole machine. Due to the gear meshing, the vibration characteristics of gear rotor system and simple rotor system have a fundamental difference. The main difference is the gear rotor system has a bending-tensional coupling vibration. Neglecting the effect of coupling vibration, it will not only cause low precision, but also lose some important information, such as the new frequencies of mode coupling. Therefore, it will be very important to conduct the research on the coupling geared rotor system from the point of view of system.Considering the static transmission error of the gears, a general three degree of freedom dynamic model of a helical gear pair was established. Combining with the rotor systems, a finite element model of the multi-shaft helical gear rotor system was determined. This paper analyzed the inherent characteristics and dynamic response of the system. Based on the linear research and considering the nonlinear effect of backlash, time-varying mesh stiffness, a more realistic nonlinear coupled gear system model was established through the describing function method. The dynamic equations of system were solved by use of variable step Runge-Kutta numerical method to obtain the results of dynamic response, which were analyzed and compared, and discussed the effect of several dynamic parameters on the dynamic characteristics of the system.Firstly, based on the gear system dynamics theory, the mechanism of inner dynamic excitation and time-varying mesh stiffness was elaborated. The gear mesh error was analyzed and the model of the static transmission error was built.Secondly, considering the static transmission error of the gears, input and output torque and so on, a general three degree of freedom dynamic model of a helical gear pair was established. Meanwhile, considering the nonlinear effect of backlash, time-varying mesh stiffness, a nonlinear gear system model was established through the describing function method, and the forced response analysis method of nonlinerar was provided.Thirdly, the unbalance vibration response characteristics of flexural-tensional expander system were analyzed by ANSYS. In accordance with separation magins obtained from inherent characteristics and API617 standard, we can judge whether the system is safe or not.Fourth, in the case of coupled gears and uncoupled gears, unbalanced response curves of system and the phenomenon of maximum vibration were analyzed. In contrast to the inherent characteristics, the generation mechanism of resonance peaks of the geared rotor system is identified. Meanwhile, the effect of system dynamic response caused by systematic parameters such as bearing stiffness and helix angle is analyzed.Finally, the solution of nonlinear dynamic equations are presented. Combined with the time-domain diagram, phase diagram, Poincare map and the FFT graph, the dynamic reaponse of system under different spin speeds, input torques, and the variation of damping ratio is analyzed. Meanwhile, the gear mesh ratio in iterative process is calculated. The phenomenon of gear system generating from bifurcation to chaos is clarified, also with the reason of gear system from unilateral and bilateral impact shock state.In this paper, dynamic characteristics of geared rotor systems were studied, and also large relavent results of dynamic characteristics were obtained, which can provide the basis for preventing the big vibration of the system, and also give the guiding significance to the design and fault analysis of the gear system.