Study On Vibration Reduction Characteristics Of Marine Steam Turbine Rotor-Seal System

Marine steam turbine unit is the core power device of the ship and one of the main sources of vibration and noise of the ship.As the key rotating part of marine steam turbine unit,the vibration noise generated by rotor will directly affect the vibration noise level of the whole system.Seal is the important component in the rotor system of marine steam turbine unit,and seal is one of the major technologies to significantly reduce rotor vibration and restrain the instability of the rotor system due to its flexibility in installation on the rotor.At present,the characteristics and laws of the influence of seal on the transmission of ship steam turbine rotor vibration to the foundation have not yet been figured out.Therefore,it is of great significance for vibration reduction design of marine steam turbine to study the seal dynamic characteristics and the vibration reduction characteristics of marine steam turbine rotor-seal system.This paper analyzes and studies the dynamic characteristics of three types of labyrinth seals and two types of new damper seals.And it studies the effect law of internal structure parameters on dynamic characteristics of seal.According to the results,the law of the vibration reduction characteristics of the system composed of marine steam turbine rotors and seals with different types and internal structures is studied.Major works are listed as follow:Numerical simulation model of seal dynamic characteristics based on perturbation method is established.Aiming at solving the dynamic characteristics of labyrinth seal,it is realized by adopting circular vortex trajectory based on the rotor seal analysis software SEAL2D/3D.Aiming at solving the dynamic characteristics of damper seal,it is realized by using Solid Works,ANSYS ICEM CFD and FLUENT as technical support and using the single-frequency elliptical vortex model and related numerical methods as theoretical support.The dynamic characteristics of labyrinth seal are studied.Based on the numerical simulation model of seal dynamic characteristics established by perturbation method,the dynamic characteristic coefficients of see-throughtype,staggered-type and stepped-type labyrinth seal is calculated.In order to guide the design of labyrinth seal structure,the effect law of internal structure parameters on dynamic characteristics of labyrinth seal is studied by changing internal structure parameters such as cavity depth/step height,seal clearance and cavity width.The dynamic characteristics of damper seal are studied.Based on the numerical simulation model of seal dynamic characteristics established by perturbation method which includes establishment of three-dimensional geometric model of seal fluid region,construction of structural mesh,setting of boundary conditions and loading of vortex displacement signals and extraction of fluid excitation force,the dynamic characteristic coefficients of honeycomb damper seal and fully-partitioned pocket damper seal is calculated.In order to guide the design of damper seal structure,the effect law of internal structure parameters on dynamic characteristics of damper seal is studied by changing internal structure parameters such as seal clearance,seal hole depth and radius of sealing hole peripheral circle of honeycomb damper seal,cavity depth and basic cavity width of fullypartitioned pocket damper seal.A simplified dynamic model of marine steam turbine rotor-seal-bearing system is established and the vibration reduction characteristics of system are analyzed.The calculated seal dynamic characteristic coefficients are substituted into the simplified mechanical model of the marine steam turbine rotor-seal-bearing system,and the vibration reduction of the system composed of the marine steam turbine rotor and the seal under different types and different internal structural dimensions are simulated.According to the law of vibration characteristics,the seal type with good damping effect and the corresponding internal structure size are obtained through comparative analysis,which can provide support for the design of the damping performance of the marine steam turbine rotor-seal system.