Research On Torsional Vibration Analysis And Safety Evaluation Method Of Large Turbo-generator

With the increasing demand of electricity, the construction of large power grid constantly advance and the structure of grid gradually become more complex. Meanwhile, duing to the requirements of efficient and environmental protection, large turbogenerator gradually replace small units and the structure of Turbine is more complex. Complex structure of grid and unit structure makes turbogenerator torsional vibration problems frequent and severe electromechanical coupling torsional vibration will cause serious damage to turbine generator shaft, cause serious accidents and crew huge economic losses, affect the normal operation of generators and power systems. This paper study problems of large turbogenerator torsional vibration, the main contents include:Firstly, the large turbine generator shaft torsional vibration modeling and the method of torsional vibration inherent characteristic analysis is studied. This paper proposes a method of establishing turbine shaft torsional vibration model, including methods for establishing continuous quality models, multi-lumped mass model and simple lumped mass model. In the perspective of the sensitivity of shaft torsional vibration inherent characteristics, taking into account the shafting torsional vibration characteristics of unit during operation may change, this paper proposes a turbine generator shaft torsional vibration model adaptive method which lays the foundation of turbogenerator torsional vibration analysis accuracy. Meanwhile, the paper also analyzes the calculation method of the unit shaft torsional vibration inherent characteristics and the method is validated. Examples show that while the method is applied to turbine generator shaft torsional vibration analysis, we can get accurate results.Secondly, the large turbogenerator torsional vibration mechanism and causes of failure were studied. This paper analyzes the failure mechanism of torsional vibration unit and common cause of torsional vibration failure. Turbine torsional vibration failures are analyzed in detail using analysis of FTA and FMEA which gets the fault tree of torsional vibration fault, analyzes the features of each cause, analyzes the hazards of fault. At the same time the reason for each failure characteristics were quantified. This paper presents a method to identify turbogenerator torsional vibration cause of failure, lays the foundation for torsional vibration fault monitoring, early warning and diagnosis.Finally, the large turbine generator shaft torsional vibration safety evaluation method is studied. This paper proposes two kinds of turbine generator shaft torsional vibration response analysis method. At the same time, the paper focuse on the use of finite element analysis software on the unit shaft coupling simulation analysis, get the non-linear relationship between equivalent stress of dangerous parts of turbine shaft couplings with the torque change, fit non-linear curve and the relation, propose a set of method of shafting coupling stress response analysis under torsional vibration fault. The paper also describes the method of the unit shaft torsional vibration fatigue life loss estimation. According to the results of shafting stress response, the paper evaluates unit shaft torsional vibration safety which ensure the safe and stable operation of turbine.