Research On Transfer Behaviour Of Unbalance Response In Rotor System

Unbalance is one of the main causes of vibration in turbo-generator unit that may lead to catastrophe failture during operation. It is hot point that enhancing balance efficiency. Because of the frequency complexity of unbalance , the unbalance response characteristics of rotor system is one of the widely researched discussions in the nearly years.Based on the former researches, the Jeffcott rotor system with mass eccentricity is analyzed in this paper. The modeling method of rotor system and bearings are presented, and the unbalance response is resolved by Riccati transfer matrix method. Based on the calculation model set up by Riccati transfer matrix, a kind of program on how to calculate unbalance response is carried out. Useing this kind of program, we make calculation analysis to the unbalance response of high pressure rotor of 200MW turbine-generator, some useful conclusions have been made also.Two examples are presented as examples to introduce the abnormal vibration during balance work. Reasons are analyzed in detail. We conclude that unsymmetric support dynamics is the main reason for this phenomenon. Both the 1st and 2nd vibration mode can be excited simultaneously by symmetric or anti symmetric unbalance distribution. Unbalance response characteristics changes a lot compared with the symmetric support condition. This conclusion is important for rotor balance in the field.Vibration phase is the important parameter to be considered during rotor balance, especially for rotor high-point decision. Due to that in most cases, the phase difference between the vertical phase and the horizontal vibration phase isn't always 90°, the high-points decided by vibration signals in two direction are usually different. In this paper, a mathematical model and a test rig were set up to research the phase change rule during run up process. We found that unsymmetrical dynamics of bearing in the two directions is the main reason for the phenomenon. We also found that when rotor runs up through the critical speed, not only it's phase but also the phase difference change acutely.Lastly the unbalance response characteristics are studied with a test rig.