Theoretical And Experimental Research On Movement Mechanism Of Floating Ring Seal In The Turbopump

Floating ring seals are used to further improve the efficiency of liquid rocket engines.With the ability to follow the rotor motion,the clearance of floating ring seals is much smaller than that of fixed annular seals.Therefore,the floating ring seal significantly reduces the leakage flowrate and improves the engine efficiency.In order to clarify the motion mechanism of the floating ring seal and the influences on the rotor vibration,in this paper,a transient fluid excitation model in the seal clearance is introduced,a dynamic model of the floating ring seal is established,the motion mechanism of the floating ring seal,the method for predicting the self-locking area is introduced,the influence of the self-locking position on the rotor vibration is studied,and the whirling motion of the floating ring seal when it is not locked up and the influences on the rotor vibration are studied.The main research content includes:For arbitrary movement between the floating ring seal and the rotor,a transient bulk flow model is introduced with the characteristics of fluid movement in the clearance,and the transient fluid excitation in the clearance is calculated.The study shows that the bulk flow model can accurately calculate the turbulence resistance and flow field in the clearance.The accuracy of the bulk flow model is almost the same with the CFD method.The transient bulk flow model has good agreement with the test result,and the accuracy of the transient bulk flow model is higher than the perturbation bulk flow model.To study the movement mechanism of the floating ring seal,a dynamic model of the floating ring seal is established,the characteristic of the floating ring seal is studied,the method of predicting the lock-up area is proposed according to the variation of the hydrodynamic force in the clearance.The studies show that the floating ring seal has the ability to follow the rotor whirling motion and approach the rotor whirling center.When the friction force is large enough,the floating ring seal follows the rotor motion and eventually locks up.The self-locking position depends on the initial motion conditions and the movement process.When the friction is insufficient,the floating ring seal finally follows the rotor whirling motion.The stable whirling motion is independent of the initial conditions and the movement process.To study the interaction between the floating ring seal and the rotor,a dynamic model of the floating ring seal and rotor system is established.The dynamic characteristic of the floating ring seal in the system is studied.The influence of the self-locking position for the floating ring seal on the rotor vibration is studied and the method of evaluating the lock-up area in the system is proposed.The studies show that the self-locking position is determined by the motion process of the rotor and the floating ring seal.The steady-state whirling motion is independent of the initial conditions and the motion process.The farther the self-locking position is from the center of the rotor support,the more eccentric the rotor whirling center offset is and the more anisotropy the rotor vibration is.The interaction between the floating ring seal and the rotor increases the lock-up area in the system.The quasi-steady whirling model is introduced for the whirling motion of the floating ring seal and rotor system.The root distribution of the quasi-steady whirling model and the stability of the whirling motion are studied.The influences on the whirling motion of the floating ring seal are studied.The influences of the floating ring whirling motion on the rotor whirling motion are studied.The studies show that the root of the steady whirling motion is unique when friction is insufficient to lock up the floating ring seal.With the increase of the seal mass,the centrifugal inertial force increases,the amplitude of the whirling motion for the floating ring seal increases,and the lag angle with respect to the rotor increases.With the increase of friction,the amplitude of whirling motion of the floating ring seal decreases,and the lag angle increases.As the rotor whirling amplitude increases,the whirling amplitude of the floating ring seal increases.Near the critical rotational speed of the rotor,the floating ring seal can effectively reduce the vibration of the rotor.With the friction increasing,the rotor whirling amplitude decreases and the phase angle decreases.With the sealing mass increasing,the whirling amplitude of the rotor decreases and the phase angle increases.A test rig for measuring the motion of the floating ring seal is developed,and the test procedure is detailed.With different pressures and rotational speeds,the whirling motion and the lock-up position of the floating ring seal are measured.With the comparison between the theoretical and experimental data,the dynamic model of the floating ring seal and the method for evaluating self-locking area are verified.