Spiralc Computational Analysis of Spirally Grooved Gas Face Seals
COST: $5,000 Executable + GUI  (2012)

SPIRAL GROOVE FACE SEAL OPERATION
Spiral groove face seals (SGFS) offer numerous advantages over conventional non contacting mechanical seals. Grooves etched on the mating ring of the sealing surfaces do not wear from contact while rotating, greatly lessening the need to overhaul machines for seal replacement. Dry (gas lubricated) operation allows the face seal to perform with less complicated and expensive external support systems like those required for oil lubricated seals. The use of tandem and double sealing arrangements with inert buffer gases allow application of the SGFS in machines handling highly volatile process fluids with virtually zero leakage to the atmosphere.

METHOD of ANALYSIS
The laminar flow of an isothermal, ideal gas on the thin film lands of a grooved face seal is described by the Reynolds equation for isoviscous fluids (no fluid inertia effects) where a successive approximation allows solution of the non-linear flow equation.

The zeroth-order equation describes the fluid flow field for a rotor static equilibrium position providing the leakage flow rate, load capacity and drag torque, while the first-order equations govern the fluid flow for small amplitude axial motions determining the force coefficients due to rotor axial motions.

Numerical Method of Solution: Finite Elements

PROGRAM FEATURES
The  program calculates the static load and dynamic axial force coefficients for gas spiral grooved face seals (SGFSs).

Configurations: Grooved stationary or rotating surface. Seal dams inside the I. D. or outside the O.D. help increase the load capacity of SGFSs.

Geometry: (See Figures 1.) I.D., O.D., grooved ID, grooved O.D., ridge clearance, groove depth

Number of grooves: 1 < Ng < 30

(a)

(b)

Ridge width ratio:

Groove (helix) angle: (Radial grooves b = 90°)

Specified Boundary conditions: I.D. Pressure & O.D. Pressure, or no I.D. flow (thrust bearing).

Fluid: Viscosity, density

Spiral calculates:

  • Seal leakage or flow rate
  • Friction torque (drag power dissipation)
  • Load capacity (opening force) and restoring moments.
  • Axial stiffness and damping dynamic force/moment coefficients due to small amplitude shaft axial and angulation motions about a static equilibrium position for a given set of frequencies.

Limitations and Restrictions:

Laminar, isothermal flow with isoviscous, compressible fluids without fluid inertia effects

PROGRAM OPERATION

Input: ExcelŽ GUI

Output: ExcelŽ GUI

Language: Fortran90. Source code NOT provided.