Meshing characteristics of geared rotor system in integrally geared compressor with unbalance excitation

The influence of unbalance on the meshing characteristic of the geared rotor system in an integrally geared compressor is investigated. Firstly, a scaled structure of the geared rotor system in an integrally geared compressor is taken as the research object, and its dynamic model is derived by a finite element method where nonlinear mesh excitation is considered. Then, based on the dynamic model, the meshing forces under unbalance effect are calculated, as well as the variation of meshing forces and the vibrations of the system under different loads and transmission errors. The results show that the side band frequencies of the rotor vibration signals have some correlation with the collision of the gear teeth. The more intensely the teeth collide, the more complex are the sideband frequencies. The frequency components are related to the center frequencies and the unbalance excitation frequencies, and the meshing state can be diagnosed according to the side band frequencies. In addition, the nonlinear gear meshing force has strong correlation with the acceleration of the box in frequency domain, but less influence on the displacement of rotor, which are verified by the test results. The results show it is a feasible approach to use the spectrum signature of acceleration on the box as essential evidence to judge the geared rotor system’s running state with unbalance excitation, which will be helpful in the vibration control and condition monitoring of the equipment.