Upgrade XLTRC2 Computational Model for Hydrodynamic Journal Bearings – Thermal Effects

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Upgrade XLTRC2 Computational Model for
Hydrodynamic Journal Bearings Thermal Effects
Thermohydrodynamic Analysis of Hydrodynamic Fluid
Film Bearings
Luis San Andres Mast-Childs Professor
TRC Project 32513/1519 T4
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XLPresDm
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CODE GUI proposed additions enhancements

• NO thermal effects (mechanical energy dissipation
  and transport by lubricant)
• NO changes in clearance due to thermal and
  mechanical deformation effects.
• Outdated I/O operations with Fortran code NOT
  efficient.
• No informed guess for starting calculations.

Known Issues with XLPresDm
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Geometry for bearing pad with preload
Nomenclature c pad clearance cm assembled
clearance e journal eccentricity
?
Pad center
rpc-cm preload, rp 0, cylindrical pad rp
c, journal and pad contact
Bearing center
rp
Y
?
?l
e
Pad with preload
journal
Film thickness
?p
?t
X
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Nomenclature P film pressure h film
thickness m viscosity, fn (T) W journal
speed
Film thickness viscosity
c pad clearance rp pad preload eX, eY
journal eccentricity
Major assumption Viscosity is average across
film thickness Laminar flow
Boundary conditions Pad leading edge, QQl. P
PS (supply pressure) trailing edge,
QQt. P Pa 0 (ambient pressure) Pad
sides, z /- ½ L, PPa (ambient) Film
pressure Pgt Pcav (oil cavitation pressure)
Reynolds Equation for laminar thin film flows
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Assemble system of equations, impose boundary
conditions and solve
FEM for solution of Pressure field
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• Nomenclature
• T film temperature
• h film thickness
• U,W circ. axial flow velocities
• m, r, Cp viscosity density, specific heat
• hB, hJ heat convection coefficients
• TB, TJ bearing and journal temperatures
• W journal speed

Major assumption Integrate energy transport
equation across film. Neglect temperature
variations. Use bulk-flow velocities and
temperature. Laminar flow
CONVECTION DIFFUSION DISSIPATION (Energy
Disposed) (Energy Generated)
Thermal Energy Transport in thin film flows
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TT(Q)
Source of energy
Sink of energy

• Numerical solution uses
• Upwind scheme.
• as are a function of flow rates

Algebraic equation for transport of film
temperature
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Ti
Heat flow Q h A (TS Ti)
A wetted area for heat transfer
Ts
h heat convection coefficient, a function of
Nusselt , oil conductivity and hydraulic
diameter (clearance). Nusselt depends on
flow conditions (Prandtl and Reynolds )

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Nomenclature F flow T temperature l
thermal mixing coefficient 0.80 (TYP)
Finlet Fsupply l Fup
Flow balance
Finlet Tinlet Fsupply Tsupply l Fup Tup
Energy balance
WR
Fup Tup
Finlet Tinlet
Downstream pad
Fsupply Tsupply
Upstream pad
Thermal mixing at pad trailing edge
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Fortran code complete L. San Andres full
development graduate student
worked for 4 months (no progress)
GUI (Excel interface) To be done NO student
available (UGS quit
after 1 month) integration with XLTRC2
expected by end of summer 08.
Examples for calibration (pressure and
temperature fields) oil 360 deg journal bearing
Dowson et al. (1966) Ferron, Frene,
Boncompain (1983) Costa, Fillon (2000
2003) oil two pad arc journal bearing
Costa, Fillon (2000 2003) Brito, Fillon
(2006, 2007)
Pressure dam bearing Childs et al (2007, 2008)
Load capacity force coefficients
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Ferron,J., Frene, J., and R. Boncompain, 1983, A
Study of the Thermohydrodynamic Performance of a
Plain Journal Bearing Comparison Between Theory
and Experiments, ASME Journal of Tribology, Vol.
105, pp. 422-428,
Load
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Test data
Film temperature
Midplane pressure
Pressure and temperature fields 4 kRPM, 6 kN
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Test data
Eccentricity ratio (e/c) vs Sommerfeld
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Test data
Peak film pressure vs. eccentricity ratio (e/c)
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Test data
Peak film temperature vs. eccentricity ratio (e/c)
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Brito,F.P., Miranda, A.S., Bouter, J., and
Fillon, M., Frene, J., and R. Boncompain, 2007,
Experimental investigation on the influence of
Supply temperature and Supply Pressure on the
Performance of a Two-Axial Groove Hydrodynamic
Journal Bearing, ASME Journal of Tribology, Vol.
129, pp. 98-105,
Load
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Film temperature
Midplane pressure
Journal locus
Test data
Predictions
e/c0.43 f 56 deg 1.35 kW 3.0 LPM 28 bar max
Pressure and temperature fields 4 kRPM, 10 kN
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Al-Jughaiman, and Childs, D., 2007, Static and
Dynamic Characteristics for a Pressure-Dam
Bearing, ASME Paper GT2007-25577
Missing details on bearing geometry, lubricant
and feed conditions. Even with test data at hand,
not able to reproduce test results in paper. VERY
PECULIAR THERMAL EFFECTS
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Fortran code complete
GUI (Excel interface) in progress
Delivery at end of Summer 08

• Complete Excel GUI(s) and interface with XLTRC2
• Enhance code to include prediction of fluid
  inertia (mass) coefficients
• MAY Include changes in operating clearance due to
  thermal effects and shaft rotation

Upgrade to XLPresDm
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GT2007-25577 Power loss
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145 psi
Journal eccentricity vs specific pressure
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145 psi
Attitude angle vs specific pressure
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145 psi
Direct stiffness KYY vs specific pressure
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145 psi
Direct stiffness KXX vs specific pressure
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145 psi
Cross stiffness KXY vs specific pressure
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145 psi
Cross stiffness KYX vs specific pressure
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145 psi
Direct DAMPING CYY vs specific pressure
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145 psi
Direct DAMPING CXX vs specific pressure
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145 psi
Cross DAMPING CXY vs specific pressure
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145 psi
Cross DAMPING CYX vs specific pressure
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Whirl frequency ratio WFR vs specific pressure
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Budget from TRC for 2008/2009
Support for programmer (GUI)
25,000 Total Cost 25,000

• Complete Excel GUI(s) and interface with XLTRC2
• Enhance code to include prediction of fluid
  inertia (mass coefficients)
• Include changes in operating clearance due to
  thermal effects and shaft rotation

BUDGET for Upgrade to XLPresDm
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Major assumption In oil lubricated bearings,
temperature does not vary across axial
length, TT(Q).
Integrate energy transport equation along axial
length to obtain
Energy transport equation (temperature invariant
along axial direction)
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In oil lubricated bearings, TT(Q).
Thermal energy advected by fluid flow
Mechanical Power Energy conducted to B J
Mechanical energy dissipation
Heat flow into bearing and journal
Axial and circumferential (bulk-flow) velocities
Thermal energy transport equation
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Questions ????
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Test data
Journal eccentricity (e/c) vs. applied static load
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(No Transcript)
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Consider small amplitude journal and pad motions
about static equilibrium position (SEP)
An applied external static load (Wo) determines
the rotor equilibrium position (eX, eY)o with
steady pressure field Po and film thickness ho
Let the journal whirl with frequency ? and small
amplitude motions (?eX, ?eY) about the
equilibrium position. Hence



Small amplitude journal motions about an
equilibrium position
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Bearing dynamic reaction forces
Damping coefficients
Stiffness coefficients
Measure of stability Whirl frequency ratio WFR
Kxy/(CxxW)
Typically No fluid inertia accounted for Force
coefficients independent of excitation frequency
for incompressible fluid. Functions of speed
load
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Dynamic reacion forces
Stiffness coefficients
Inertia coefficients
Damping coefficients
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Casing (or ambient)
TBouter
Bearing
Thermal Energy conducted to bearing
TB
Mechanical power (P ) by film shearing Torque x
W
Exit flow carrying thermal energy
Thermal Energy conducted to / from journal
Journal
W
TJ
L