Analysis On The Dynamic Characteristics For A 1000MW Power Station Turbine-driven Induced Draft Fan Set

The 1000MW power station turbine-driven induced draft fan set is the large key equipment, and its important feature is the original independent multiple rotor-bearing systems interacted through the gear mesh. At present, the studies on geared multi-rotor system are still relatively less. Therefore, the modeling and vibration analysis on geared shafts of the 1000MW power station turbine-driven induced draft fan set, which is driven with two-stage gears decelerating, are made and the calculation methodology, which is suitable for engineering applications and includes the bending vibrations, torsional vibrations and lateral-torsional coupling, has been formed. The main contents are divided into four parts.(1) Establish the linear and nonlinear dynamic model with geared shafts.Considering the structural characteristics of various components, concentrated mass, centralized mass moment of inertia distribution, material characteristics and gear parameters, bearing parameters, clutch type, etc, and basing on the actual data of shafts, the dynamic models of turbine-gear-induced draft fan (including clutches) system are established, which include the approximately calculated linear dynamic model and the nonlinear dynamic model with the nonlinear factors considered.(2) Analysis on the vibration characteristics of geared shafts.Considering the gyroscopic moment, the main critical speeds and vibration modes of each order bending vibration, torsional vibration and lateral-torsional coupling of turbine, induced draft fan, gear-clutch-induced draft fan subsystem and the whole system, are analyzed, and the impacts on the inherent characteristic of the variation of cross stiffness and damping, gearbox support stiffness and gear meshing stiffness are studied.(3) Analysis on the unbalance response of geared shafts.The coupling effect for gear and clutch, and nonlinear characteristics can make new dynamic characteristics of the system, such as the torsional vibration caused by bending vibration, lateral-torsional coupling, etc. Based on the engineering practice, the unbalance and unbalanced position are established, and the unbalance responses with the presence of unbalance are analyzed. Therefore, the dynamic response graphs of each key node of turbine, gear, clutch, induced draft fan and all unbalance key nodes, are made and the effect of structural damping to the system unbalance response is studied.(4) Analysis on the nonlinear response in the unbalance excitation.Considering the gyroscopic moment, the coupling effect of gear and clutch, and the time varying meshing stiffness of gear pair, etc, the nonlinear dynamical equations are established and the fixed interface synthesis method is used to reduce the dimension of freedom, the unconditional convergence Newmark-β method is used to solve the key nodes’ responses of turbine and induced draft fan. All the key nodes’ time-domain waveforms, axis orbits and amplitude-frequency response curves are analyzed and the nonlinear effects of gear backlash and gear meshing stiffness are studied.