THRUST

Program THRUST Overview

The steady operating characteristics of hydrodynamic thrust bearings are of interest to both designers and users of fluid film thrust bearings. The operating characteristics of interest include the temperatures in the bearing, the film thickness distribution in the plane of the pad, pressure distribution in the film, elastic deformations in the pad and runner, power losses, and flow requirements. Program THRUST predicts these and other characteristic quantities for hydrodynamic thrust bearings.

Tilting pad and fixed geometry bearings can be analyzed by the program. Point, line, and mechanical pivots can be specified for tilting pad bearings. Fixed geometry bearings that may be analyzed include the tapered-land, parallel tapered-land, and complex tapered-land styles.

The user may have the program iterate on film thickness to match load, may specify a fixed film thickness but not pad tilt angles, or may specify both film thickness and pad tilt angles.

Models

Pressure Distribution in Tilting Pad Bearing Advanced models in the program include:

• Temperature and pressure dependent viscosity
• Cross-film viscosity variation
• Cavitation, groove mixing, sump temperature
• Turbulence
• Fluid centrifugal inertia
• Machined crowns
• Runner misalignment
• 3-D film temperature model
• 3-D heat conduction in the pad
• 3-D mechanical-thermal elasticity in the pad
• Axisymmetric heat conduction in the runner
• Axisymmetric elasticity in the runner
• Various boundary conditions for heat transfer, elasticity, and pressure solutions.

Computation

THRUST makes use of the finite element method to solve the coupled partial differential equations leading to the operating characteristics. The 2-D Reynolds equation governs the pressure distribution and is solved using quadrilateral elements. This equation is coupled reciprocally to the film temperature solution which is solved with 3-D brick elements. The film temperature solution is coupled to the conduction solutions in the bearing solids; brick elements are used in the pad while axisymmetric triangular elements are used in the runner. The Reynolds equation solution is also coupled to the elasticity in the solids; brick and triangular axisymmetric elements are used in the pad and runner, respectively.

Output

THRUST produces an ASCII output file with the solutions to the governing equations, easy to read significant max/min values, and various non- dimensional quantities. In addition, graphical interface files are produced to allow easy viewing of the pressures, temperatures, and deformations.

Hardware/Software Requirements

THRUST can be run on a DOS-based IBM compatible PC with an 80386 CPU and at least 8 MB of RAM. Due to the amount of computation, however, a faster computer is highly recommended. In addition, since finer finite element meshes are desirable, a computer with 32- 64 Mb of available RAM is recommended.

THRUST writes to file the results from the analysis in a format compatible with the finite element graphical program Tecplot(TM). If graphical output of this form is desired, the user may opt to purchase the graphics program.

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