Research On The Characteristics Of Coupled Machine And Electric And Waterpower Vibration Of The Main Shaft System In A Hydro-turbine Generating Unit

The power and dimension of hydro-turbine generating unit has been sharply increasing, at the same time, ratio rotational speed has been increasing correspondingly,the vibration and stability problem of hydro-turbine generating unit are standing out gradually, which had been noticed greatly.The main shaft system is the most important components of hydro-turbine generating unit, the vibration problem of shaft system is the key issue to solve for design, manufacture and maintain of hydro-turbine generating unit.The shaft system of hydro-turbine generating unit is a complicated rotor-bearing system, the vibration and stability problem of shaft system considering all kinds of affecting factors is concerned. A dynamics model of shaft system of hydroelectric machines is developed on the base of taking into account the gyroscopic effect, angular inertia, shear deformation of the shaft, position of guide bearing, the damping of the guide bearings, inertia of the water in the runner etc, and the unbalanced magnetic pull of the generator, and hydraulic forces of the runner acting on rotor externally can be considered in the calculating model. The vibration characteristic of mechanical and electrical coupled systems of the generators rotor, free vibration characteristics and transverse dynamic characteristic of the shaft system of hydro-turbine generator unit were researched in this paper, aim to find out the coupled vibration mechanism of shaft system,which would provide theoretical and technical instruction for optimizing the structure and controlling the vibration of shaft system of electric generating set.The main contents of the paper as follows:(1) The nonlinear vibration of mechanical and electrical coupled systems of rotor shaft of the generators is investigated. The lateral-torsional coupling vibration of rotor system of a hydro-turbine generator unit caused by transitional electro-magnetic force and moment was studied in this paper. A mathematical model on the lateral-torsional coupling vibration was established, the dynamical characteristics of lateral-torsional coupling vibration of rotor system were investigated on the numerical computations, and effects of rotating speed and rotating eccentricity on the lateral-torsional coupling vibration of rotor shaft of the generators are studied in detail. The influence of the amplitude-frequency response curves of the different parameters is researched. Therefore, if the operation state of the system falls into the sensitive area of the mechanical and electromagnetic parameters, a strong vibration will be induced due to the parametric resonance.(2) Free vibration characteristics of the main shaft system of hydro-turbine generator unit are investigated.Based on the parameters of the main shaft system of an actual electric generating set, the lateral vibration mechanical model of shaft system is created using the finite element method (FEM), and the natural frequency, critical speed and mode shape of transverse revolving vibration of shaft system are calculated.influenees of variation of guide bearing rigidity on critical speed and modal vibration mode of transverse vibration are analyzed.(3) The transverse dynamic characteristic of the main shaft system of hydro-turbine generator unit are investigated. The vibration of shafting system of hydroelectric machines is induced by machine and electric and waterpower. The nonlinear dynamic sketch of the shafting system is established, the vibration differential equation of the shafting system is developed on the base of taking into account the characteristic of the oil-films of the guide bearings and the unbalanced magnetic pull of the generator, as well as taking into account the influences of eccentric mass force of the Rotor and water turbine runner, unbalanced force of water encouraging. The dynamic response of system is solved on the numerical computations under the different eccentric mass force. Effects of eccentric mass on the vibration of shafting system are studied in detail. This model can provide the theoretical reference and the emulate calculation for the dynamic analysis and design of shafting system of hydroelectric machines.