T Slot Dynamic Gas Film Seal A Low Speed Gas Film Force Characteristic Research

End face gas lubricated mechanical seal, short for dry gas seal(DGS), is an advanced non-contacting mechanical seal technology. With the characteristics of no-friction running, low leakage rate, long service period, high efficiency, the DGS is widely used for shaft seal in high speed and high pressure running fluid mechinery of petroleum chemical industry. In recent years, the DGS technology is used in some lower speed running equipments, such as agitators and reaction vessels. When the DGS works at low speed condition, the slip flow effect of the gas film between the seal end faces must be considered. The T-groove dry gas seal (T-DGS) has a symmetric structure of the groove geometry, which enables it to rotate bi-directionally. Therefore, the engineering application scope of the T-DGS is growing gradually. However, at present, the research on the steady and dynamic performance of the T-DGS is relatively rare.The Reynolds Equation, the governing equation of the gas film between the seal faces was analyzed with the small perturbation method, and the slip flow effect was taken into account, obtaining three equations, including a steady Reynolds Equation, and two dynamic Reynolds Equations. The three Reynolds Equations were changed into the dimensionless forms, and were decretized with a finite differential method. The iterative expressions of the steady pressure field and the dynamic pressure field of the gas film between the seal faces were given. The equations were solved with a successive over relaxation method (SOR). The steady performance parameters, such as the dimensionless open force and dimensionless leakage rate, and the steady performance parameters, including axial gas film stiffness coefficient and axial gas film damping coefficient were calculated.An calculation example of the T-DGS was chosen to investigate its steady performance and dynamic performance. The effect of slip flow, the key geometry parameters of T-groove, and the operating parameters of the DGS on the steady performance was analyzed. It was shown that the slip flow effect made the open force weaker, and made the leakage rate larger. The key geometry parameters of T-groove, including groove number, Ng, groove depth hg, ratio of larger groove arc length to a calculating doman arc length in the circumferential direction, γ, ratio of smaller groove arc length to the larger groove arc length in the circumferential direction, γ1, ratio of larger groove length to a calculating doman length in the radial direction, ζ, ratio of smaller groove length to the larger groove length in the radial direction, ζ1, have some effect on the open force and leakage rate. When γ, γ1, and hg equal to3μm,0.6,0.6, respectively, the open force would reach the largeat values, while the leakage rate was larger too. As the compressibility number and operating difference increased, the open force and leakage rate would increase too. By adopting the multiple linear regression method, some empirical formulae considering the effect of the key geometry parameters of T-groove, slip flow effect, and DGS operating parameters on the steady performance parameters were fitted.Effect of the slip flow, the key geometry parameters of T-groove, and DGS operating parameters on the dynamic performance parameters were analyzed. It was shown that the slip flow effect made the axial gas film stiffness coefficient smaller. When the frenquency number was small, it would decrease the axial gas film damping coefficient. The key geometry parameters of T-groove, including hg, γ, γ1, ζ, ζ1, have significant effect on the dynamic performance of the T-DGS.