Analysis of a Radial Groove Gas Face Seal

An outside-pressurized, bi-directional, gas face seal is analyzed here. This seal face is made up of a hydrodynamic section, consisting of alternate regions of land and groove, and a hydrostatic dam. The groove region, based on its optimum width, can have either parallel or radial side boundaries, depending on the cost of machining and tooling. The compressible Reynolds equation is solved over a radial groove hydrodynamic section by both finite difference and finite element methods. The former 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 1-D viscous flow. Thus, the pressure distribution over the entire seal interface and the seal leakage are determined for a given film thickness. Finally, the separating force is obtained as a function of film thickness for a given design, allowing the operating point to be predicted.