XL_ThrustBearing^®: A Computational Physics Analysis Tool for Tilting Pad Thrust Bearings (both regular and self-equalizing types).

Sponsors: 1. Texas A&M Turbomachinery Laboratory (2016-2017), 2. Texas A&M University Turbomachinery Research Consortium (TRC, 2017-2019) Goal: To build a comprehensive computational tool for prediction of the static and dynamic load performance of thrust bearings and further integrate it into XLTRC2^® software package. Resources: 1. XL_TRC2^®.

XL_ThrustBearing^® Software tool

Features:

Analysis in both SI and US metric system. Analysis for tilting pad (1D and 2D tilting, rocker back and flexure pivot) and fixed geometry (taper land) TBs. 2D hydrodynamic pressure: Accounts for cross film viscosity variation. 3D temperature in the fluid film (thermal energy transport equation). Analysis in both laminar and turbulent flow regimes. 3D heat conduction in a pad with specified sides’ temperature. Temperature dependent oil viscosity.

In-house Finite Element model of pad temperature induced (thermal) and pressure induced (mechanical) deformations: High accuracy. Simplified analytical model for pad temperature and pressure induced deformations based on Euler Bernoulli beam theory: Rapid analysis. Accounts for Babbitt or liner (PEEK or PTFE) pad top layer in both thermal and pad deformation analyses. Pivot stiffness is included in the frequency reduced model for a variety of commonly used pivot types. Perturbation Analysis: Delivers equivalent frequency reduced force coefficients (stiffness and damping) for thrust collar axial displacements.

NEW in v 3.0, Analysis for self-equaling tilting pad thrust bearings. Multiple-pad analysis: Accounts for thrust collar misalignment (tilt angle). Accounts for friction forces acting at the contact area of the leveling plates. Implements leveling plates geometry model from commercial 3D modeling packages: Eliminates geometry simplification. Hertz contact analysis: Delivers peak pressure and deformation at the leveling plates contact points and pivot.

Analysis Output:

Minimum film thickness and pads’ tilt angles. Drag power loss and drive torque. Demand for supply flow rate. Peak pressure and maximum pad temperature. Flow condition: laminar or turbulent. Pivot deflection . Peak pad deformations, induced due to pressure and temperature changes. Bearing axial stiffness and damping coefficients.

NEW in v 3.0, Leveling plates tilt angle and displacements. Forces and moments acting on the leveling plates. Peak pressure and deformation at the contact lines of the leveling plates. Pressure and deformation at the pivot of the leveling plates.

• Along with 2D and 3D graphs showing the operating characteristics, e.g. fluid film thickness field, pressure field, fluid film temperature field, pad deformation fields.

Validation of Predictions

Versus Ansys^®:

Predictions of pad top surface elastic deformations for (top) a cylindrical pivot TPTB, and (bottom) a spherical pivot TPTB. Comparison between commercial software and in-house FE model (graphs in middle and right side). Supply temperature = 46°C, Rotor speed = 3 krpm and specific load = 1.0 MPa.

Versus Test Data:

a) Pad temperature rise

TEHD predicted pad subsurface temperature rise derived from both a laminar flow model and a turbulent flow model vs test data for a six-pad TPTB [30]. Supply temperature = 46°C.

b) Pressure field TEHD predicted oil film pressure along the circumferential length of the pad at the 25% (top) and 75% (bottom) of the radial length vs test data for a six-pad TPTB operating under 0.5, 1.0, 1.5, and 2.0 MPa of specific load per pad. Rotor speed = 3 krpm, supply temperature = 40 ˚C.

c) Film Thickness TEHD predicted oil film thickness at the mean radius of the pad leading edge (top) and trailing edge (bottom) vs test data for a six-pad TPTB. Supply temperature = 40 ˚C.

Further Predictions from XL_ThrustBearing^® for an Example Self-Equalizing Tilting Pad Thrust Bearing

Predicted fluid film thickness field (left) and pressure field (right) for a TPTB of (a) regular type, (b) self-equalizing type without including contact friction forces, and (c) self-equaling type with contact friction forces included. Bearing operates with 0.01° thrust collar (static) misalignment. Rotor speed = 4krpm, specific load per pad = 2 MPa, µ= 0.2.

Predicted fluid film temperature field (left) and pad temperature field (right) for a TPTB of (a) regular type, (b) self-equalizing type without including contact friction forces, and (c) self-equaling type with contact friction forces included. Bearing operates with 0.01° thrust collar (static) misalignment. Rotor speed = 4krpm, specific load per pad = 2 MPa, µ=0.2.

Predicted fluid film temperature field (left) and pad temperature field (right) for a TPTB of (a) regular type, (b) self-equalizing type without including contact friction forces, and (c) self-equaling type with contact friction forces included. Bearing operates with 0.01° thrust collar (static) misalignment. Rotor speed = 4krpm, specific load per pad = 2 MPa, µ= 0.2.

Predicted pad minimum fluid film thickness for self-equalizing TPTB operating under light to heavy applied loads vs sliding friction coefficient. Bearing operates with 0.01° thrust collar (static) misalignment. Applied load per pad = 1 MPa to 3 MPa and rotor speed = 4krpm.

Predicted fluid film pressure on a pad for self-equalizing TPTB operating under light to heavy applied loads vs sliding friction coefficient. Bearing operates with 0.01° thrust collar (static) misalignment. Applied load per pad = 1 MPa to 3 MPa and rotor speed = 4krpm.

Predicted pad mechanical deformation for self-equalizing TPTB operating under light to heavy applied loads vs sliding friction coefficient. Bearing operates with 0.01° thrust collar (static) misalignment. Applied load per pad = 1 MPa to 3 MPa and rotor speed = 4krpm.

Publication à Learn more:

1. Koosha, R., and San Andres, L., 2019, “Effect of Pad and Liner Material Properties on The Static Load Performance of A Tilting Pad Thrust Bearing,” ASME Turbo-Expo 2019, Paper No. GT2019-90231 (Recommended for journal publication).

2. R. Koosha, L. San Andrés, 2019 “On the Static Load Performance of a Large Size, Heavily Loaded Spring Supported Thrust Bearing”, STLE 74th Annual Meeting & Exhibition, May 19-23, Nashville, Tennessee, USA.

3. San Andres, L., and Koosha, R., 2018, “A Thermo-Elasto-Hydrodynamic (TEHD) Computational Analysis of Tilting Pad Thrust Bearings: Analytical and FE Pad Structure Models,” Annual Progress Report to Turbomachinery Research Consortium, TRC-B&C-01-018, Texas A&M University, College Station, USA. URL: http://hdl.handle.net/1969.1/175255.

4. San Andres, L., and Koosha, R., 2017, “Thermo Hydrodynamic (THD) Computational Analysis for Tilting Pad Thrust Bearings (TPTBs),” Annual Progress Report to Turbomachinery Research Consortium, TRC-B&C-05-017, Texas A&M University, College Station, USA. URL: http://hdl.handle.net/1969.1/175131.

Original by Rasool Koosha (September 2019)