Research On The Dynamic Characteristics Of Labyrinth Seal-rotor Bearing System

Labyrinth seal is a kind of seal commonly used in industry.It is an important part of rotating machinery.It is widely used in high temperature,high pressure and high speed rotating machinery.The influence of sealing characteristics on high-speed rotating machinery has been paid more and more attention.If the seal does not work properly,it will cause fluid leakage,leading to serious safety accidents.When the fluid passes through the labyrinth seal,there will inevitably be many uncertain factors,which will produce uncertain excitation.The fluid excitation force acts on the rotor,which affects the stability and reliability of the sealed rotor system in practical application,and has a significant influence on the dynamic characteristics of the rotor subsystem.In this paper,the uncertainty of a straight-through labyrinth seal-rotor bearing system is considered.The dynamic characteristic coefficient fluctuation of a straight-through labyrinth sealed rotor bearing system under the influence of random uncertain excitation is studied.On this basis,the rotor dynamic characteristics of labyrinth seal-rotor bearing system are studied.The main research contents and results are as follows:(1)In a typical cavity,the fluid dynamics equation is composed of continuity equation and circumferential momentum equation.The random excitation in the x and y directions of the rotation axis can be represented by bounded noise.The bounded noise excitation is substituted into the circumferential momentum equation and the fluid dynamics equation with random uncertain excitation is established.(2)Due to the influence of random excitation,the orbit of the rotor center will not rotate along the stable elliptical orbit as previously studied.Using the Thomas model.On this basis,the orbit of the rotor center is represented by the combination of elliptic trajectory and bounded noise excitation.A Thomas model method for calculating the dynamic characteristic coefficient of labyrinth seals was established.(3)Combined with the proposed fluid dynamics equation and the labyrinth seal exciting force model,the dynamic characteristic coefficient of the rotor system was calculated by writing a calculation program with Matlab.The fluid excitation force of labyrinth seal is analyzed,and the excitation force is concentrated in the rotor shafting system.Based on this,the disturbance clearance function,cavity coefficient and seal excitation force under the influence of uncertain excitation are derived.The simulation results with uncertain excitation of different intensities are compared with the traditional results under ideal conditions.The influences of random factors on the dynamic characteristic coefficient of labyrinth seal-rotor bearing system under different rotor speed,inlet/outlet pressure ratio and inlet swirl velocity were analyzed.Generally speaking,the deviation level of the dynamic characteristic coefficient is directly related to the uncertain excitation intensity,and is usually positively related to the random excitation intensity.(4)The theoretical dynamic characteristic coefficient and the dynamic characteristic coefficient under the influence of uncertain excitation were applied to the rotor dynamics analysis software Madyn 2000.The rotor dynamics analysis of labyrinth seal-rotor bearing system in air compressor is carried out.The effect of random excitation intensity on the dynamic characteristics of the system is studied.The first two critical speeds of the labyrinth seal-rotor bearing system are more sensitive to the random excitation intensity,which is similar to the influence of bearing support stiffness on the critical speeds of the labyrinth seal-rotor bearing system.The seal excitation force has obvious influence on the amplitude of the labyrinth seal inlet and outlet,the rotational speed decreases when the maximum value of the first order vibration occurs.So the influence of random excitation can’t be ignored when studying the rotor dynamics of labyrinth seal system.