Research On Dynamic Characteristics Of Liquid Hydrogen Turbopump Rotor-seal System

With the rapid development of modern industry, the increases of the speed of therotor shaft, seal pressure and rotor flexible degree, and the decrease of the seal clearance,the problem of seal incentive is more strict in rotor shafting design. To a reasonabledescription of sealing fluid exciting force is not only beneficial to the system dynamicsanalysis, simplified analysis process, but also to clear seal structure parameters on thesystem of physical meaning, revealing the influence law of sealing fluid exciting force.In this paper, sealing fluid exciting force model is established, throughthree-dimensional CFD study a type of pressure distribution, fluid force, and liquidhydrogen turbopump rotor-labyrinth seal system dynamics model is set up, the study onits dynamic characteristics, stability analysis system, studies the influence law. Themain research contents and results are as follows:(1) Use Muszynska model and experience on the basis of introducing parameters,consider seal entrance prewhirl effect, and establish a set of Muszynska model tocalculate the labyrinth seal experience parameter method to obtain the complete sealingfluid exciting force theory model, analysis of labyrinth seal fluid exciting force, andlump the exciting force on rotor shaft system.(2) A type labyrinth seal three-dimensional fluid calculation model is set up, usingFluent fluid calculation software analysis the internal flow and pressure distribution,and research the influence of seal clearance, rotor eccentricity on seal leakage and theeffect of vibration force. Through the calculation data for sealing the excitation modeldesign experience in nonlinear regression parameters, determine the experiencecoefficient. The study found that seal fluid exciting force is by a combination of staticpressure and dynamic pressure, in general, hydrostatic pressure of leading role.(3) Combination of labyrinth seal experience exciting force model, the calculatedmodel parameters to obtain complete sealing exciting force model, using the finiteelement method to establish liquid hydrogen turbopump rotor-labyrinth seal systemdynamics model for numerical solution. Research found that bearing supportingstiffness, the place of bearings does not effect the modal of shafting vibration mode;Labyrinth seal fluid exciting force of shafting vibration, its frequency close to thefirst-order natural frequency and cause resonance, leading to liquid hydrogenturbopump rotor-labyrinth seal system instability.(4) By studying the liquid hydrogen turbopump rotor-labyrinth seal system stability,it is found that with increasing shaft bearing supporting stiffness, the increase in the sealclearance, seal medium viscosity increased system stability enhancement; With the increase of seal pressure difference on both ends, sealing radius increases, system iseasy to instable; The parameters of seal change little on the shaft critical speed, thesupport stiffness of seals is far less than the support stiffness of shaft bearing, the impacton the critical speed can be ignored.