Method Study On Reliability Optimization Method Of Turbine-Generator Units By Considering Dynamic Stiffness And Dynamic Strength

Hydraulic turbine-generator units will appear strong vibration phenomena under complex excitation such as flow excitation, electromagnetic excitation and mechanical unbalanced forces. The strong vibration of hydraulic turbine-generator units will lead to large dynamic deformation and dynamic stress, which seriously affect the stiffness and strength, as well as the safety and reliable operation of hydraulic turbine-generator units. Therefore, when analyze the reliability of units, not only the effect of static stiffness and static strength of the units should be considered, but also the effect of dynamic stiffness and dynamic strength caused by the vibration of units should be considered. This paper takes the hydraulic turbine-generator units as an object, comprehensively considering the effect of dynamic stiffness and dynamic strength of main shaft system reliability, and more deeply analyze reliability optimal design method of hydraulic turbine-generator units.By using finite element method, the dynamic characteristics of hydraulic turbine-generator units are analyzed, and the nonlinear dynamic model of the units is established. Based on the dynamic equation, dynamic characteristics of units are explored by applying multi-scale method. The influence of uncertain parameters on dynamic characteristics of units is revealed by analyzing the gradient of flow excitation, mechanical unbalanced forces and electromagnetic excitation.Considering the effect of dynamic stiffness and dynamic strength caused by vibration of units, the expression of total deformation and stress of main shaft system is established. Considering the randomness of units, analyzing the stiffness failure model, strength failure mode and multi-failure mode, dynamic reliability models of hydraulic turbine-generator units under stiffness failure model, strength failure model and stiffness-strength failure model are established. The reliability optimization design method of hydraulic turbine-generator units by considering dynamic stiffness and dynamic strength is established.Using modified first-order second-moment method, the dynamic reliability sensitivity expression of hydraulic turbine-generator units is established by based on dynamic reliability mode of units, and the internal relation between dynamic reliability of units and its structure parameters, hydraulic parameters and electromagnetic parameters is revealed.Taking structure parameters of main shaft system of hydraulic turbine-generator units as design variables, the minimum volume of main shaft as design objective function, the reliability requirements as the constraint, reliability optimization design mathematical model of main shaft by considering dynamic stiffness and dynamic strength is established. Finally, reliability optimization design method of hydraulic turbine-generator units by considering dynamic stiffness and dynamic strength is confirmed.An example is presented and the above mentioned dynamic reliability optimization design method is simulated to verify the correctness of the theoretical research in this paper.