Analysis of a Radial Groove Gas Face Seal

Abstract

An outs&-pressurized, bi-directional, gas face seal is analyzed here. This seal face is mude up of a hydrodynamic section, consisting of alternute regions of land and groove, and a hydrostatic dam. The groove region, based on its optimum widfh, can have either parallel or radial side boundaries, depending on the cost of machining and tooling.The compressible Reynolds equution is solved over a radial groove hydrodynamic section by both finite difference and finite element methodr. The fonner algorithm is seen to be about two to three times faster than the latter, but there is room for improvement in both.Next, a finite element solution is obtained over a corresponding parallel groove geometry. Both geometries yield approximately the same results, other parameters remaining equal. Hence, for design optimization purposes, a radial groove approximation may be justified for a parallel groove design in order to use the faster and easier finite difference algorithm.The flow over the hydrostatic section is modeled as I-D uiscous --

Performance Evaluation of Bidirectional Dry Gas Seals with Special Groove Geometry

“…In addition, the inverse Knudsen number is [16] defined as: Free molecular flow Typical pressures assumed in the study of the gas seals usually are in the range of few MPa. For instance, relatively higher operating pressures of 2.1MPa [11] and 4.5MPa [4] as well as low pressures of around 0.3MPa [7] are reported in the literature although higher pressures of up to 40-55MPa can be encountered in current day applications. Depending on the operating temperature and film thickness, these would result in Knudsen numbers that can be higher than the given range for continuum flow with no slip conditions.…”

“…Depending on the operating temperature and film thickness, these would result in Knudsen numbers that can be higher than the given range for continuum flow with no slip conditions. It is noted that a typical temperature of 300K is assumed in the analyses conducted in [3][4]11]. For these conditions, continuum flow with slip boundary condition may be assumed, for which the common form of Reynolds equation, for instance, cannot be generally used.…”

“…Over the years, several different bidirectional groove designs have been suggested, including radial/parallel grooves [11], bidirectional tapered step grooves [12], three-row spiral grooves [13] and T-shape grooves [14]. The seals with bidirectional grooves of square and/or rectangular geometries are relatively easy to manufacture, although they may need a larger number of grooves to generate the desired load carrying capacity.…”

Thermohydrodynamics of bidirectional groove dry gas seals with slip flow

“…Viscous and boundary friction ℎ Film thickness ℎ 0 Minimum film thickness ℎ Critical film thickness ℎ ,1 , ℎ , 2 Relative depths at the triangular and middle trunk parts of the grooves ℎ Convection heat transfer coefficient ℎ , , ℎ , Convection heat transfer coefficient from outer rims of rotor and stator Thermal conductivity of the gas Thermal conductivity of seal ring material …”

“…Basu [2] investigated the performance of various groove geometries for bidirectional seals, including the radial or parallel groove profiles. Takeuchi et al [3] introduced bidirectional tapered-step grooves, and a three-row spiral groove configuration was presented by Wang [4].…”