Study On Dynamic Performance Of Supercritical Carbon Dioxide Dry Gas Seal

The operating pressure of S-CO₂ dry gas seal is high.Under high parameter operating conditions,if the shaft vibrates violently,it is easy to cause dynamic instability and leakage increase of S-CO₂ dry gas seal,and even cause seal failure when it is serious.At present,the research on S-CO₂ dry gas seal mainly focuses on the steady-state performance,but rarely on the dynamic performance.In view of this,this paper takes S-CO₂ dry gas seal as the research object,and deeply studies the dynamic characteristics,dynamic follow-up and transient performance of S-CO₂ dry gas seal after considering different turbulence models.Firstly,the dynamic lubrication model of S-CO₂ dry gas seal with variable viscosity and variable density was established.The dynamic Reynolds equation was derived by using the small disturbance method and displacement velocity increment method.The dynamic characteristic coefficient of S-CO₂ dry gas seal was solved by using the finite difference method.Then,considering the support spring stiffness and O-ring damping when the static ring was installed flexibly,the dynamic characteristic system obtained in the previous research work was used.Finally,based on the above research,the distribution of transient membrane pressure disturbance of S-CO₂ dry gas seal was studied and analyzed.And then the transient sealing performance was solved.And the parameters of different working conditions,structural parameters and working conditions were analyzed.The influence of mechanical element characteristic parameters on the dynamic performance of S-CO₂ dry gas seal was studied.The results show that,when other parameters are unchanged,the pressure and dynamic coefficients of the end face film modified by turbulence are larger than those based on laminar flow assumption.The maximum pressure of the surface film after Constantinescu correction is the largest,Hirs are the smallest.And the transient film thickness disturbance value and transient membrane pressure disturbance value are opposite.Within the scope of this study,regardless of turbulence correction,the dynamic characteristic coefficient of S-CO₂ dry gas seal increases with the increase of speed,pressure or amplitude,and decreases with the increase of taper.According to the influence of structural parameters on the dynamic characteristic coefficient of S-CO₂ dry gas seal,it is suggested that the number of grooves be8～16 and the groove depth be 11～13μm,the helix angle is 24～33°,the ratio of groove length to dam length is 0.7～1.1,the ratio of groove width to abutment width is 0.5～0.9.The abrupt change of the film thickness|Δh（r,θ）|_max at the initial moment of excitation increases with the increase of the rotating speed and the mass of the stationary ring,and decreases with the increase of the pressure.The maximum value of periodic variation after sudden change decreases with the increase of rotating speed,static ring mass and pressure.The maximum perturbation of film thickness|Δh（r,θ）|_max increases with the increase of spring stiffness,O-ring damping and taper,and decreases with the increase of wave amplitude.At the initial time,the dynamic opening force and leakage rate increase with the increase of speed,mechanical element parameters and taper,and decrease with the increase of pressure and amplitude.The amplitude of sinusoidal variation decreases with the increase of speed,pressure,mass and amplitude of stationary ring,and increases with the increase of spring stiffness,O-ring damping and taper.The equilibrium value of sinusoidal variation increases with the increase of speed,pressure and amplitude,but decreases with the increase of taper.