The Surface Roughness Of The Sealing Surface Affects The Performance Of The Spiral Groove Dry Gas Seal

With the in-depth study of dry gas seal and its wide application in industry,more and more attention has been paid to the manufacturing error of sealing surface.Generally,the sealing surface considered is a rough surface with unevenness,and its characteristic size is on the order of micrometers or below.In fact,the gas film between the end faces of dry gas seal is extremely thin(generally 2μm ～ 5μm),which is basically in the same order of magnitude or only one order of magnitude different from the surface roughness.Therefore,the influence of surface roughness and gas slip flow efficiency on the sealing performance of spiral groove dry gas seal(S-DGS)can not be ignored.Up to now,the research on the influence of sealing surface roughness and slip flow effect on the sealing performance of S-DGS is not enough.Although a few scholars have studied the influence of individual factors on the sealing performance of S-DGS,there is no systematic analysis on the synergistic effect,interaction effect and influence on fluid flow among various factors.In view of this,this paper takes the spiral groove dry gas seal which is the most widely used in practice as the research object.Based on the gas lubrication theory,the Reynolds equation is deduced by using the micro element analysis method in cylindrical coordinates,and the mathematical analysis model of spiral groove dry gas seal is established.Considering the factors of surface roughness and slip flow effect,the extended average Reynolds equation under compressible fluid condition was modified by introducing relevant correction factors,and the Reynolds equation suitable for analyzing the influence of surface roughness,slip flow and their combination factors on the sealing performance of S-DGS was obtained.Then the finite difference method is used to solve the problem,and MATLAB software is used to compile the corresponding calculation program to obtain the gas film pressure.Finally,the other sealing performance parameters of S-DGS are further analyzed.In this paper,the influence of single factor surface roughness,multi factor surface roughness and slip effect on the sealing performance of S-DGS was studied in detail.The results show that the influence of the surface roughness of spiral groove sidewall on the sealing performance of S-DGS can be ignored only considering the influence of single factor surface roughness.The surface roughness of the end face and groove bottom has a great influence on the opening force and leakage rate of the sealing gas,especially when the surface roughness of the spiral groove end face is less than 0.1μm,the gas sliding flow effect is significant,and the influence of the surface roughness of the end face on the sealing performance of S-DGS is more obvious.When considering the surface roughness ofmulti-factors,the surface roughness of spiral groove end face and groove bottom exist at the same time,and they have the greatest influence on the sealing performance of S-DGS.