Research Of Nonlinear Dynamics About Dry Gas Seal In Rotor System

In rotary machinery with dry gas seal as shaft seal,the dry gas seal device is not only affected by the natural vibration of the seal system itself,but also affected by the oil film force of the impeller rotor and bearing.Long time high frequency and high speed vibration may cause the seal element to wear and damage,or even cause the seal to fail.Therefore,in order to ensure the stability,safety and reliability of the equipment,the large system should be taken as the object when the dry gas sealing effect is studied.This paper takes the rotor-bearing-dry gas seal system as the background,and mainly takes the dry gas seal static ring as the research object.By studying and analyzing the axial vibration of the static ring in different parameters of the system,the axial stability of the dry gas seal system is discussed.Firstly,taking the dry gas seal as the research object,the static ring-gas film seal system is modeled simply and the motion equation is presented.The nonlinear expressions of gas film stiffness and damping are derived.Under specific working conditions,the nonlinear expressions of stiffness and damping under different parameters were obtained by using MAPLE software by taking the Angle and number of spiral grooves as variables.The Runge-Kutta method in MATLAB was used to solve the motion equation of static ring-gas film under different parameters.By comparing the time history diagram and phase trajectory diagram under different parameters,it can be seen that the vibration displacement first decreases and then increases with the increase of the number of slots.When the number of slots n=12,the nonlinear vibration displacement of the static ring is the smallest.When the spiral groove Angle is taken as the variable,the nonlinear vibration displacement of the static ring is minimized when the Angle is 78.41°.Based on the above research,the structure of rotor-bearing-dry gas seal system is simplified and modeled.Simplify the rotor-bearing body to a damped spring.The effects of structural parameters of dry gas seal and rotor-bearing performance parameters on the seal performance of rotor-bearing-dry gas seal system are discussed.Taking the number of spiral grooves,spiral groove Angle,bearing stiffness and bearing damping as variables,MATLAB software was used to solve the two-degree-of-freedom vibration equation to study the vibration of static ring under different parameters.By comparing the time history diagram and the phase trajectory diagram,it can be seen that the number of slots has almost no effect on the vibration displacement of the static ring in the large system.With the change of the Angle of spiral groove,the following property of stationary and static ring becomes better and worse until the seal fails.In a certain order of magnitude,the axial vibration displacement of the static ring increases with the increase of the bearing stiffness.At a certain order of magnitude,the increase of bearing damping slows down the return of the static ring to its initial vibration state.Due to the influence of the rotor-bearing system,the vibration displacement of the static ring under the rotor-bearing-dry gas seal system is much larger than that under the consideration of the dry gas seal system only.Then,the optimal spiral groove Angle and instability critical point Angle of static ring vibration are obtained by repeated fitting calculation with MAPLE and MATLAB software.And the value of pressure coefficient f is changed.As f increases,the vibration displacement of the static ring increases at the optimal spiral groove Angle.At the critical instability point,chaos occurs.