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.
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XLHYDROJET® Cost: $ 7,500
(US) |
Licensed by
Turbomachinery Laboratory – |
|
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, |
|
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, |
|
Fluid
properties / Shear flow model |
Laminar, laminar
to turbulent transition and fully developed turbulent bulk-flow model on thin
film flow configurations. |
|
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 |
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