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STATUS OF THRUST FOIL BEARINGS
RESEARCH FOR OIL-FREE MACHINERY
Travis CableResearch Engineer, PXG
Luis San AndrésMast-Childs Chair Professor
May
2018
BEST PAPER AWARDS 2003,2005, 2008, 2010, 2012 IGTI S&D – Microturbomachinery
High speed gas bearings for oil-free machinery
2002 2018: Multiple sponsors:
NSF, NASA GRC, Capstone MT,
Honeywell, Borg-warner, US NAVY,
TRC
FY 02-18 total: +$ 2M +Test rigs: $250 k+ Software license: $ 120k
Tested multiple foil & metal mesh bearings
4 PHDs + 4 MS + 2UGs/year.
35+ journal papers & many invited lectures
Max surface speed (130 m/s: 70 krpm). Max
dyn. load 100 lbf @ 500 HZ
Status of Thrust Foil Bearing Research
• TRC sponsored effort to
bring metal mesh thrust
foil bearings (MMTFB) to
a commercialization level (Fall of 2015 -Summer 2017).
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• Rayleigh-step MMTFB proved unsuccessful, while another
design worked: a tapered TFB supported a moderate load
W/A~ 3.75 psi.
• TRC & PI funds produced a fully operational test rig for thrust
foil bearings.
• Research with MMTFB continued (unfunded) until the end of
2017.
Existing Test Rig for Thrust Foil Bearings
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A Test Rig for Thrust Foil Bearings
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Shaft Speed, RPOΩ 40 krpm, 212 m/s
Drive Motor Torque 1.1 N.m
Bearing OD Limit 102 mm
Static Load 0 - 580 N
Dynamic Load 0 – 100 N
Cooling Flow 0 – 500 SLPM
Specifications Capabilities:
For specified applied load, shaft
speed, and cooling flow
• Static break-away torque and lift-
off drag torque
• Bearing static stiffness (load vs
deflection)
• Dynamic axial force coefficients
• Pad Temperatures
A RAYLEIGH-STEP METAL MESH
THRUST FOIL BEARING (MMTFB) AND
ITS FAILURE
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Assembled Metal Mesh Thrust Foil Bearing
Dimensions Support Mesh
Material 316 S-Steel Copper
Inner Diameter 45.72 mm 50.8 mm
Outer Diameter 120.65 mm 120.65 mm
Thickness 9.53 mm ~0.40 mm
Rayleigh Step Top Foil
Material 316 Stainless Steel
Coating Parylene® N
Coating Thickness 3 μm
Number of Pads, NPAD 6 [-]
Outer Pad Diameter, DPO 101.6 mm
Inner Pad Diameter, DPI 50.8 mm
Pad Arc Extent, θP 45 °
Step Depth, hS 19 μm
Top Foil Thickness, ttf 0.127 mm
6-Pad Metal Mesh Foil Thrust Bearing
6-Pad Bump Type Foil Thrust Bearing [1]
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.
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Tests with Rotor Speed (Summer 2017)
Rotor brought to 40 krpm and MMTFB pushed against thrust collar
(applied load W/A=7 kPa).
Drag torque increased quickly with
time and pad #3 showed a
temperature rise of ~30 C in 15 s
solid contact & burnt!
.
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Failure of Three Prototype MMFTBs
• Tests with three Rayleigh-step top foils and three sheets of 40
OPI mesh produced solid contact between top foil and rotor
collar.
• Rubbing burned top foils and removed steps.
• Failure due to waviness of mesh and lack of anchor on
leading edge of top foils (windage effect).
Back to Basics
TAPERED PAD
METAL MESH THRUST FOIL BEARING
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Single pad (55 arc)
coated with MOS2
Three 40 OPI metal mesh creates a taper
height of ~0.12 mm.
Thermocouple locates just before the transition
from taper to land section.
.
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Test with Tapered MMFTB (six pad)
• At rotor speed 40 krpm, load in steps applied
to target 5 psi (35 kPa). (300 SLPM cooling)
• A load maintained for 60 s; torque increases
in steps but temperature increases steadily.
• Contact for W/A > 3.6 psi (26 kPA)
contact
kPa
New Proposal
MEASUREMENT OF LOAD
CAPACITY, DRAG TORQUE
AND TEMPERATURE IN A
THRUST FOIL GAS BEARING
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New Proposed Work 2018-2019
1. Revamp test rig with intermediate shaft between the
router motor and thrust collar improve alignment.
2. Test a Trust Foil Bearing from Oil-Free Turbomachinery.
3. Measure TFB load capacity and drag torque and top
foil temperature vs. rotor speed vs. cooling flow.
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Budget
Support for graduate student (20 h/week) x $ 2,200 x 12 months $ 26,400
Fringe benefits (2.4%) and medical insurance ($422) x 12 months $ 5,698
Tuition & fees three semesters (24 ch) $ 13,275
Conference travel and registration $ 1,800
Supplies: bearing parts and rig ancillary parts $ 2,827
Total BUDGET $ 50,000
MEASUREMENT OF LOAD CAPACITY, DRAG TORQUE AND TEMPERATURE IN A THRUST FOIL GAS
BEARING
Test program will continue to show commitment of TAMU-TL, supported
by TRC, to develop sustainable and energy efficient oil-free
turbomachinery.
Questions (?)
Thanks to TRC for past support
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