Research On Dynamic Characteristics And Operation Reliability Of Hydro-Generator Unit Under Complex Flow Excitation

Under the combined action of powerful and complex hydraulic,electric and magnetic,the hydro-generator unit will generate seriously complex vibration,which will bring huge potential safety hazard to the safe and stable operation of the unit itself.Especially when the unit operates under off-design conditions,the flow excitation also has significant non-stationary characteristics,which makes the vibration of the unit more complex.In addition,each part of the unit inevitably has the relationship of mutual connection and mutual influence,which makes the hydro-generator unit often perform some unexplained abnormal behaviors during operation.Therefore,in order to improve the safety,stability and reliability of the hydro-generator unit during operation,it is necessary to develop the research on dynamic characteristics and operation reliability of the unit under the influence of complex flow excitation.The main contents of this paper include:Firstly,the main shaft system is simplified as a lumped parameter model by considering the influence of the bearing system on the unit and introducing the influence of the air gap magnetic field force of the generator on the unit,and the runner blades are simulated by the flat shell element.According to this,the general lumped parameter finite element hybrid dynamic model of the hydro-generator unit is established by using the theories of rigid body dynamics and elastic dynamics.Then,the dynamic equation expression of the unit is given by using the Lagrange equation.Secondly,by analyzing the flow excitation characteristics of hydro generating units under different working conditions,the mathematical models suited for simulating the flow excitation of hydro-generator unit under different working conditions are proposed based on the virtual excitation method.Then,according to the established lumped parameter finite element hybrid dynamic model of hydro-generator unit,the dynamic characteristics of the unit under different working conditions are investigated by using the random vibration theory,and the inherent relationship between vibration characteristics and structural parameters,material parameters and hydraulic parameters are revealed.Then,the flow excitation characteristics and dynamic characteristics of the unit under different working conditions are analyzed by an example,which lays a theoretical foundation for the study of the operation reliability of the unit.Then,according to the safe and reliable operation criterion that the vibration amplitude of each part of the hydro generator unit should be controlled within a certain limit value,the limit state control equations of vibration of each part are given.The reliability models of the hydro-generator unit under rated load condition,partial load condition and overload condition are established by applying the first exceeding reliability theory,respectively.Based on this,the comprehensive reliability evaluation model of the hydro-generator unit under complex working conditions is constructed by combining the models of each working condition.Finally,the internal relationship between the unit operation reliability and various structural parameters,material parameters and hydraulic parameters is explored by an example,and the feasibility and effectiveness of the reliability model is verified by using the Monte Carlo simulation(MCS).