Nonlinear Vibration Characteristics Analysis For Shaft System Of Hydraulic Generating Set Under Multi-source Excitation

With continuous increase of energy demands for our country,it is accompanied by the expansion of the scale of power system and the diversification of energy structure.As a renewable clean energy,the proportion of hydro-power in entire energy system is increasing,and its impact on the stable operation of power grid is gradually raising.Therefore,the operation stability of hydro-power units has became one of the hot issues in the field of water conservancy and hydro-power engineering.In-depth analysis of the vibration mechanism of hydro-turbine generator unit can better ensure the reliability of its operation,and effectively avoid or reduce the possible harm of vibration failure to the units.In this paper,the shaft system of hydro-turbine generator set is taken as the research object,and the rotor dynamics theory and nonlinear numerical analysis method are adopted.From the perspective of quantitative analysis,the non-linear dynamic behavior and motion stability of the shafting system under various external excitations,such as nonlinear oil film force,rubbing force,sealing force and unbalanced magnetic pull considering dynamic and static eccentricities,are analyzed numerically.The main research contents are as follows:(1)Aiming at the shortcoming of the establishment of UMP models without the influence factors of dynamic and static eccentricities in past,based on the geometric relationship between stator and rotor,a unified expression of the air gap length considering the compound eccentricities is derived,the UMP model with compound eccentricities is developed using the principle of motor magnetic field analysis and Maxwell stress integral.Based on this mechanical model,the impact of rubbing faults and electromagnetic excitation on the coupled bending and torsion dynamic characteristics of hydro-turbine generator system are analyzed systematically.(2)Aiming at the rubbing problem of stator and rotor caused by mechanical and electromagnetic factors,a nonlinear dynamic model and corresponding differential equation of rotor-bearing system under the combined action of unbalanced magnetic pull,rubbing force and nonlinear oil film force are constructed,and corresponding dynamic characteristics are numerically analyzed.Methods such as bifurcation diagram,Poincaré map,and axis trajectory diagram are used to analyze the non-linear characters of system on the domains parameter including excitation current,rotor mass eccentricity,and stator radial stiffness.(3)In view of the nonlinear vibration problem caused by excitations of multiple vibration sources in the shaft system of hydro-generator unit,a coupled bending and torsional vibration model of the unit shaft system under combined actions of nonlinear sealing force and unbalanced magnetic pull considering both dynamic and static eccentricities factors is constructed.The numerical analysis methods are adopted to study the dynamics characteristics of system,and the vibration characteristics on the electromagnetic parameters,mechanical parameters,and sealing parameters are emphasized.The comparison with the coupled bending and torsion vibration models of the unit only consider the generalized air gap eccentricity is given.In this paper,the nonlinear vibration characteristics of shaft system from hydroelectric set under the hydraulic-mechanical-electrical excitation are analyzed.The conclusions can provide a theoretical basis for the fault diagnosis and vibration control of hydroelectric set,and provide a useful reference for its optimal design.