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CFD Seal Analysis Industrial Codes
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Foundation :: Engineering Applications :: CFD Seal Analysis Industrial Codes

CFD Seal Analysis Industrial Codes

Analysis of Turbomachinery Seals

CFD Seal Analysis Graphic Moderators:
Don Shaffer

source code available SOURCE CODE AVAILABLE

Future aerospace and air breathing systems will require improved seals to enhance efficiency, prevent leakage, control lubricant and coolant flow, prevent entrance of contamination, inhibit the mixture of incompatible fluids and assist in controlling rotor response. CFD Seal Analysis Industrial Codes was developed to analyze a wide variety of turbomachinery seals. The industrial codes were designed to accomplish rapid parametric analysis and design optimization.

  • GCYL, Gas Cylindrical Seals, analyzes a wide variety of cylindrical seals, such as steps, tapers and hydrostatic geometries. The code is a Reynolds equation solver that considers laminar and turbulent flow in the film region. Principal applications are for low clearance geometries, such as floating ring and circumferential sectored seals. The code produces the clearance and pressure distributions, leakage, interface loads, righting moments, viscous dissipation and frequency dependent stiffness and damping coefficients. Plotting routines are also provided for visualizing the clearance and pressure distributions. Applications include seals for compressors, industrial gas turbines and jet engines. It has also been applied to helium buffer seals for cryogenic pumps.

  • GFACE, Gas Face Seals, is similar to GCYL except it applies to face geometries.

  • SPIRALG, Spiral-groove Gas Seals, analyzes spiral-groove cylindrical and face seals. Laminar flow is assumed and isothermal and narrow groove theory is used. Forces, moments, film thickness, leakage, power loss and cross-coupled, frequency-dependent, stiffness and damping coefficients are produced. Spiral-groove seals are finding wide application in gas compressors and circulators and in computer disk drives.

  • SPIRALI, Spiral-groove Liquid (Incompressible) Seals, is based on the Hir's bulk flow model with the addition of Spiral-groove theory. Turbulence is treated with an extended form of the Hir's bulk flow model, generalized to include separate and arbitrary friction factor Reynolds number relationships for each surface. Film inertia is treated globally throughout the film. Narrow groove theory is used to characterize the spiral groove geometries, which maintains the global representation. Geometries with film discontinuities, such as parallel and multiple helical grooves, employ loss coefficients. Rough surfaces can also be modeled by applying appropriate friction factor relationships. Output includes forces, moments, film thickness, leakage, power loss and cross-coupled stiffness and damping coefficients. Pressure breakdown bushings, wearing rings and damping seals for high pressure pumps and cryogenic turbomachines can also be analyzed.

  • ICYL, Liquid (Incompressible) Cylindrical Seals, capabilities include 2-D incompressible, isoviscous turbulent flow in cylindrical geometries, rotation of rotor and/or housing, roughness of both rotor and housing and inertia pressure drops at inlets to the fluid film from the ends of the seal and from pressurized pockets. Applying a Bernoulli relation at each boundary point and reducing the static pressure by the computed kinetic energy incorporates inertia effects. Couette and Poisueille turbulence, and cavitation are included. Geometries such as steps, pockets, tapers, preloaded arcs and hydrostatic recesses can be treated. The code produces the pressure and clearance distributions, rotor position, forces and moments, pocket pressures and flows, and the cross-coupled dynamic coefficients (stiffness and damping). Applications include liquid hydrostatic and hydrodynamic seals for pumps, cryogenic machines and miscellaneous machinery. Plotting routines are also provided.

  • IFACE, Liquid (Incompressible) Face Seals, has similar characteristics as ICYL except it analyzes face seal configurations rather than cylindrical configurations.

  • KTK, Knife-to-knife Analysis of Labyrinth Seals, calculates the leakage and pressure distribution through labyrinth seals. Both straight through and step labyrinths are considered. Input data are required to describe the seal geometry and the environmental conditions affecting the leakage. Output is provided in the form of leakage flow and flow resistance characteristics, i.e., flow factor versus pressure ratio. In addition, an optimization feature is included which permits the user to identify global geometric constraints and allows the code to identify an optimum seal configuration based on minimum leakage. Both straight through and step labyrinths are considered. Applications include all gas seal turbomachinery.

  • DYSEAL, Dynamic Response of Seals, determines the tracking capability of fluid-film seals and can be used for parametric variations in geometry to improve dynamic response. The code can analyze face seals and floating ring cylindrical seals. For face seals, the rotating mating ring or shaft can be given vibrations in five degrees of freedom, consisting of three translations (x, y and z) and two rotations about the x and y axes respectively. The seal ring response is also in five degrees of freedom. The interface is represented by cross-coupled stiffness and damping coefficients that are obtained from other codes. The effects of coulomb friction of the secondary seals on seal ring response are included. Piston ring and O-ring secondary seals are input options. The floating ring seal analysis permits two degrees of freedom for both seal and ring, and is intended to determine seal ring response to an orbiting shaft. The secondary seal occurs between the ring and the wall and x-y Coulomb friction at that location is accounted for. The general method of computation is a forward integration in time that provides absolute motions in all degrees of freedom. At every time step, friction has to be evaluated to determine if motions continue or are halted.
A Graphical User Interface (GUI) was produced that couples all codes through a system executive. Input preparation is through menus, dialog boxes, and button options, and is similar to the Windows architecture prevalent in contemporary PC usage. The input files can be prepared manually using a text editor and the instructions for using the codes in this manner are included in the technical manuals for the individual codes.
CFD Seal Analysis Industrial Codes carries the NASA case number LEW-16582. It was originally released as part of the COSMIC collection.
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