Nonlinear Dynamic Characteristic Analysis And Experimental Investigation Of The Rotor-bearing System With Typical Faults

Rotating machinery plays a very important role in many sectors of national economy. With the pursuit of higher speed and higher efficiency of the rotating machinery, the rotor system as the core component operates in harsher environment, so it often breaks down. Therefore, the dynamic characteristic, vibration feature and diagnostic technology of rotor with faults are required to be researched deeply for the guidance of engineering design and fault diagnosis. In this paper, the dynamic characteristic and fault diagnosis of rotor with faults are numerically investigated by finite element method. The main contents are as follows:1. The dynamic characteristics of the rotor-bearing system supported by oil film are investigated, and the effects of all kinds of system parameters are also discussed. The results indicate that unbalance, dynamic viscosity, bearing aspect ratio and bearing clearance have great influence on rotor system. And increasing the dynamic viscosity and decreasing the bearing clearance properly can improve the stability of the system.2. A dynamic model of rotor-bearing system with rub-impact fault is established, taking the stator elasticity into account. The characteristics of the rub-impact system with elastic or inelastic stator are compared and discussed. The results indicate that the bigger stator mass and rubbing stiffness is, the greater coupling effects will happen on the rotor and stator. If the mass of the stator is much heavier than that of the rotor, rub-impact with elastic stator can be simplified as that with inelastic stator. Otherwise, rotor-stator coupling must be taken into account.3. The dynamic characteristics of the cracked rotor are investigated, and the effects of all kinds of system parameters are also discussed. The results indicate that the crack can be more easily identified in a low speed, small eccentricity rotor system or when the crack exists in the middle of the rotor. And the existence of the crack has little influence on the system unstable speed and unstable pattern.4. The crack and rub-impact fault signals are analyzed by the method of waveform, FFT spectrum and Hilbert-Huang spectrum. The vibration features of crack fault, rub-impact fault and their coupling fault are investigated systematically, and the conclutions are gotten:the displacement response of the rotor containing5X,3X and2X components reaches its maximum amplitude when its speed is at1/5,1/3and1/2of the critical speed. Hilbert-Huang spectrum identifies rub-impact more accurately and efficiently, even the slight ones that cannot be identified by FFT spectrum.5. The experimental investigation of rotor with fault is performed. The results validate the conclusions of the numerical method and provide a basis for diagnosing rub-impact fault and crack in practice exactly.6. By analyzing the rub-impact fault in the high-speed centrifugal compressor experiment, the renovation projects are submitted to avoid this failure in the next time. In the subsequent operation, the compressor can operate well at full working speed, which shows the rationality of fault analysis and the renovation projects.