Rotor Transient Balance Method

The balance problem of rotor has become a vital subject with the continuously improvement of rotating machinery in the fields of power, speed and compact structure. The application of usual methods for rotor balance meets more or less difficulties on site. Firstly, not all industrial sites are equipped with rotor balancing machines as its extremely expensive price. Secondly, trial and try experiment done in balancing process is a time consuming and costly work. The resultant inconvenience can be easily imagined. Moreover, to balance the rotor at one or more pre-designed stable rotating speeds can be hardly guaranteed in reality. In view of these difficulties, to develop a feasible and convenient rotor balancing strategy is actually a challenging and urgently needed work.The work described in this thesis is just such a contribution to the aforementioned topic, in which a novel rotor balancing method is proposed based on investigating the transient dynamic information collected in rotor accelerating process.The dynamic characteristics of rotor and their calculation methods as well as two conventional rotor balancing methods (i.e. Modal based and Influence Coefficients based balancing methods) are discussed at first and then followed by a simulated experiment on a cantilever rotor with one disc, whose critical speed and transient unbalancing response are calculated in Matlab. The detailed investigation and analysis on the computational results show that: (1). A fluctuation occurs on the rotor flexibility when the rotor goes through its critical resonant vibration zone. (2). In resonant range, the precessional velocity fluctuates around the spin velocity of the rotor. (3). After the rotor passes its resonant zone, the phase angle does not increase any more, and it begins to fluctuate around a constant value (2n+ 1)π rad. (4). The dynamic flexibility, the precessional velocity and phase angle fluctuate with the same frequency. (5). A natural and quantitative law does exist between the azimuth of the imbalance of the rotor and its spin angle, precessional angle and its phase angle. Based on those findings, a new dynamic balancing method for flexible rotor with one disc was proposed. Only two accelerating processes are required when realizing the new approach. The azimuth angle of the imbalance is identified in the first time of acceleration with the aid of the rotating angle, the precessional angle and the phaseangle. Then the unbalance extent can be determined in the second time of acceleration through the way of adding trial mass. The effectiveness and the flexibility of the proposed rotor balancing method are also verified by a practical experiment. The comparison shows that the experimental results agree very well with the simulated computational results.A preliminary discussion is further extended to the balance of the rotor with two discs.