Research On The Unbalance Response And Its Influence Factor Of Turbo-generator

With the development of turbo-generators to large-scale,flexible supports have emerged.Compared with the rigid support,the relationship between the vibration of the rotating shaft and the vibration of the bearing is much more complicated under the flexible support.Studying the unbalanced response characteristics of turbo-generator units and its influencing factors has important practical significance for shortening the fault-recovery period.Firstly,the simplified method and principle of turbo-generator shafting system were described.The finite element model of rotor-bearing system dynamics was established.The process of solving the rotor unbalance response by finite element method was introduced.Considering the influence of the support stiffness,the equivalent analysis model of the bearing-support system was established.Then,the influence of the support stiffness on the unbalanced response of the low pressure rotor of a large-scale steam turbine was studied.Results showed that as the stiffness of the support is reduced,the second-order critical speed of the low-pressure rotor is reduced from above the operating speed to within the operating speed.The reduction of the support stiffness not only affects the equivalent stiffness,but also reduces the equivalent damping.When the support stiffness is small,the vibration of the bearing is similar to the absolute shaft vibration value,which is greater than the relative shaft vibration.Under flexible support,the hysteresis angles of the vibration of the bearing is close to absolute shaft vibration,which is larger than the relative shaft vibration lag angle.Taking the double-swing rotor test stand as the research object,the static stiffness of the bearing was calculated by finite element method,indicating the anisotropy and coupling of the bearing.The identification method of bearing parameters considering anisotropy and coupling is proposed.Based on the measured frequency response function of the bearing,this method was used to identify all the dynamic characteristics of the bearing.This method uses the test points near the first-order natural frequency of the bearing seat as the feature point to identify the dynamic characteristics of the bearing.The bearing and the oil film are equivalent to one system,then the equivalent analysis model of the support system based on the measured frequency response function of the bearing is established.The frequency response function of bearing with different supporting stiffness was tested by hammering test.The variation law of frequency response function of the bearing and the equivalent dynamic coefficient of the supporting system were studied.It shows that with the decrease of support stiffness,the amplitude of the frequency response function is increasing and the equivalent stiffness and damping coefficient of the system show a decreasing trend.The support system dynamic coefficients calculated by the different models were compared.The coefficient of dynamic characteristics calculated by the two methods is similar within the second-order natural frequency,and there is a large difference between them when above the second-order natural frequency.In order to analyze the accuracy of the two calculation models,the unbalanced response of the rotor of calculation models and the experimental results were compared.The results show that both models can reflect the unbalance response of the rotor system within the second-order natural frequency,the differences between them become larger when above the second-order natural frequency.The unbalanced response of the rotor under the equivalent analysis model of the support system based on the measured frequency response function agrees well with the experimental results.The accuracy of this model is high.