Study On Dynamic Characteristics Of Marine Steam Turbine-Planetary Gear Reducer Shafting

With the continuous improvement of maneuverability,projecti le carrying ability and acoustic performance of ships in China,the Marine power system needs to develop in the direction of high output power,low space occupancy and low vibration.Among them,high power and low space occupancy refers to increasing the output power of Marine steam turbine system and planetary reducer system and reducing the volume of the system,and acoustic performance mainly refers to reducing the vibration of the system.Therefore,reducing the amplitude and vibration acceleration of Marine steam turbine,increasing the output torque of planetary reducer system,reducing the volume of the system and reducing the vibration of steam turbine and planetary reducer are the main means to solve the problem.This paper studies the vibration characteristics of herringbone differential planetary reducers and marine steam turbines using a combination of theoretical modeling,numerical simulation,and experiments.The common unbalanced mass eccentricity of marine steam turbines and complex operating conditions on the turbine shafting system are analyzed.The influence of vibration characteristics and stability,considering the coupling dynamic characteristics of marine steam turbine and planetary reducer system,the coupling vibration characteristics and mutual influence laws of the system were studied in depth.The main research contents are as follows:Using the lumped parameter method,considering the time-varying meshing stiffness,eccentric error,installation error,frequency error and initial ph ase angle of gear errors,misaligned meshing relationship between the left and right helical gears,according to the gear mesh deformation relationship to establish a five degrees of freedom herringbone gear system dynamic model of two-stage closed differential planetary gear reducer.In view of the structure characteristics of herringbone closed differential planetary gear reducer,and considering the geometrical characteristics of the contact surface of helical gear pair and the meshing tooth pitch and o ther factors,a time-varying mesh length calculation model for the involute helical gear pair is established,the time-varying meshing stiffness of helical gear pair is calculated.The influence of three kinds of errors,initial phase of error and misalignment of helical gears on the vibration characteristics of differential stage sun gear and output shaft of planetary reducer is calculated and analyzed.Considering the effects of gear gravity and clearance,the three possible meshing states of the gears in the planetary reducer are theoretically derived,the meshing deformation function of the gear is derived and the expression of the meshing force is proposed.The numerical simulation is used to simulate light or no-load conditions.The frequency response component of the multiple frequency and its harmonic frequency of the output shaft of the planetary reducer and the frequency doubling vibration mechanism are analyzed.A planetary reducer prototype test rig was built and the correctness of the theoretical model was verified by adjusting the operating conditions of the reducer.The finite element model of the rotor-bearing system is established by using Timoshenko beam theory,and the inherent characteristics and unbalanced response of the single-span Jeffcott rotor-bearing system are analyzed.The influence of the nonlinear oil film force of the sliding bearing is used to analyze the vibration characteristics of the rotor system by numerical methods.By analyzing the axial trajectory,phase diagram,spectrum diagram and Poincare map of the sliding bearing,the influence of the rotor wheel disc unbalance eccentric phase on the oil film vortex and oil film oscillation state of the sliding bearing was analyzed;The influence of the eccentric phase relationship of the disk and the misalignment of the coupling on the stability of the oil film of the sliding bearing in the spanned rotor system;by comparing the influence of the eccentric phase relationship of the disk on the oil film stability of the single-span rotor system and the multi-span rotor system,The difference between the influence of the unbalanced eccentric phase of the disk on the stability of the oil film in the single-span rotor system and the complex multi-span rotor system is revealed;considering the particularity of the marine turbine operating conditions,the floating and swinging of the ship at the working speed is studied.The correctness of the theoretical study was verified by comparing the experimental results with those of the Jeffcott rotor experiment rig.Considering the specificity of the herringbone two-stage closed differential planetary reducer structure,a marine steam turbine-planetary gear reducer coupled dynamic model is established,the coupled vibration characteristics of the syst em are studied,and the vibration characteristics of the coupled power system and the uncoupled system are analyzed.Differences in vibration characteristics,study the influence of hull floating and swing on the coupled vibration characteristics of the system,and analyze the interaction between the marine turbine and the planetary reducer system.