XLhydrojet® & XLHYDROTHRUST® Computational Analyses of hydrostatic/hydrodynamic bearings

The use of hybrid (combination hydrostatic and hydrodynamic) journal bearings and damping seal bearings as support elements in cryogenic turbomachinery and process fluid machinery has steadily grown. Fluid film bearings enable smaller and lighter turbopumps through no bearing DN life limitation and no sub-critical rotor operation. These mechanical elements have durability, low friction and wear, accuracy of positioning, and large direct stiffness and damping force coefficients. The growth of an "all-fluid-film- bearing" technology for advanced and less expensive (per launching cost) turbo pumps demands the development of analytical models and design tools, the testing of components, and the implementation of the technology.

XLHYDROJET®

Cost: $ 7,500 (US)

Licensed by Turbomachinery Laboratory –
contact Lsanandres@tamu.edu (979 862 4744)

XLHYDROTHRUST®

Cost: $ 7,500 (US)

Hydrojet: RADIAL BEARINGS, Hydrothrust: THRUST BEARINGS

Prices effective 2010

 Source code NOT provided

XLhydrojet® is not restricted just to analyze cryogenic fluid film bearings and seals. The code predictions have been validated with test data for bearings with mineral oils, water and air (perfect gas) in regimes of operation ranging from laminar flow to turbulent flows, and including the transition zone to fully developed turbulence. The industrial members of the TAMU Turbomachinery Research Consortium use the programs for their specific needs in rotordynamic analysis and troubleshooting of rotor-bearing systems.

Hydrostatic/hydrodynamic (hybrid) journal bearings handling process fluids have limited dynamic stability characteristics and their application as support elements in high speed flexible rotating systems is severely restricted. Measurements on water hybrid bearings with angled orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and null or negative whirl frequency ratios.

XLhydrojet®  calculates the static load and dynamic force coefficients for the following bearing types:

hydrostatic bearings with rectangular recesses (single recess row or side-to-side double recess row) and angled orifice injection

annular pressure seals (damping bearing seals) (cylindrical and multiple-lobe)

plain cylindrical hydrodynamic bearings (cylindrical and multiple-lobe)

fixed arc hydrodynamic bearings with arbitrary pre-load

flexure-pivot tilting-pad journal bearings (hydrostatic and hydrodynamic)

tilting-pad journal bearings

cylindrical pad bearings with a simple elastic matrix (ideal foil bearing)

 

XLhydrojet® includes the following thermal models:

adiabatic model, i.e. insulated journal and bearing surfaces

isothermal journal at specified temperature and insulated (adiabatic) bearing

isothermal bearing at specified temperature and insulated journal

isothermal journal and bearing surfaces

isothermal journal and radial heat flow through bearing (stator)

adiabatic journal and radial heat flow through bearing (stator)

XLhydrojet® calculates
1) bearing flowrate or seal leakage,
2) friction torque, power dissipation and temperature rise,
3) load capacity (fluid film forces and restoring moments),
4) stiffness, camping and added mass coefficients due to dynamic journal center displacements and journal axis rotations.
5) pressure and temperature fields on the bearing surface, and density and viscosity field variations, within ranges of fluid flow Reynolds numbers and Mach numbers.
for isothermal flow with a barotropic fluid, and
6) thermo hydrodynamic adiabatic flow and/or isothermal journal and bearing surfaces in the single phase flow regime.

as a function of
a) rotor (journal) center eccentricity and journal axis misalignment, OR b) applied external load to bearing,
c) inlet specified circumferential pre-swirl velocity distribution,
d) angle of fluid injection

and the following fluids:
1) liquid/gas hydrogen, 2) liquid/gas nitrogen, 3) liquid/gas oxygen, 4) liquid/gas methane, 5) liquid water, 6) oil, 7) air, 12) barotropic fluid.

XLhydrojet®  handles the following boundary conditions at the bearing exit planes:
(1) periodic pressure asymmetry in the axial direction,
(2) local discharge end seal effects via an orifice like model to simulate wear-ring hydrostatic bearings or annular seals,
(3) inlet specified circumferential pre-swirl velocity distribution.

The axial clearance functions included are (a) uniform, b) tapered, c) stepped, or, d) arbitrary via spline interpolation.

Cylindrical bearings may be specified as multiple lobe geometries, and bearing pads may have an assembly preload.
For (flexure-pivot) tilting-pad journal bearings, pads’ mass moment of inertia, flexure web rotational stiffness and damping coefficients are needed for full specification of the bearing geometry.

The thermo hydrodynamic analysis for prediction of the static and dynamic force response of variable properties - process fluid film bearings considers:

Equations on film lands of bearing:

Mass conservation,
Bulk-Flow momentum in circumferential and axial directions,
Energy transport equation for mean flow temperature or enthalpy
Adiabatic or isothermal journal(shaft) and bearing (stator) boundaries, or specified radial heat flow through the bearing shell.
Realistic boundary conditions including fluid inertia effects at entrance and exit flow regions.

Equations at rectangular recesses of a hydrostatic bearing:

Global mass conservation relating the orifice inlet flow, the flow from recess closure towards or from the film lands, and the rate of accumulation of fluid within the recess volume,
Global momentum in circumferential direction relating the momentum fluxes from film lands towards or from the recess closure and the inlet momentum flux due to the angled injection.
Global energy transport equation at bearing recesses with adiabatic heat flow surfaces and mechanical energy dissipation due to journal rotation.

Fluid properties / Shear flow model

Laminar, laminar to turbulent transition and fully developed turbulent bulk-flow model on thin film flow configurations.
Turbulent flow closure model: bulk-flow with friction parameters based on Moody's friction factor equations including surface roughness.
Fluid of variable properties, functions of pressure and temperature, with realistic thermophysical equations of state (NIST standard data base).

 

Numerical method of solution

Control volume - finite difference (SIMPLEC) method.

Input

MS Excel® Graphical User Interface - worksheet

Output

MS Excel® Graphical User Interface – worksheet and graphs for calculations

Language

FORTRAN77 Source code NOT provided