self-replenishing, self-repairing solid lubrication technology for fuel cells emmanuel y.a. wornyoh...
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Self-replenishing, Self-repairing Solid Lubrication Technology for Fuel Cells
Emmanuel Y.A. Wornyoh and C. Fred Higgs III
Particle Flow and Tribology LaboratoryMechanical Engineering
Dowd/ICES SeminarOctober 21, 2005
Outline of Presentation
Need for new compressor technology in fuel cells
Oil-free, self-replenishing lubrication
Proposed Research: Developing oil-free,
self-replenishing lubrication for compressor
Mobile Fuel Cell (FC) Power Systems
Benefits of Fuel Cell Compressors:
Increased fuel efficiency
Increased power density
Reduced stack size
Reduced cost
Compressed Air
Compressor** Fuel Cell*
Fuel Cell Automobile*
*Daimler-Chrysler**http://www.mechanology.com
Needs of Fuel Cell Compressors:
More powerful positive-pressures
Extreme rotational speeds (~160 mph)
Oil-free lubrication
Lubrication Mechanism for Fuel Cell Compressor
Motivation Energy efficiency
Replacing oil lubricants with powder lubricants
Freeing depleting global oil supplies
Environmental concerns Testing “green”
lubricants
Tribological Advantages Stability, sustainability in
extreme environments (-100 oC to ~800 oC)
++
U
Bearing
Shaft
h
Lube
++
U
Bearing
Shaft
h
Lube
ShaftBearing
Fuel Cell Compressor (Courtesy Mechanology,LLC)
Journal Bearing
Problem StatementNeed for a novel lubrication system for fuel cell
compressorsOil-free lubrication to avoid fuel cell stacks contaminationLubrication must be adequate at extreme speeds (~160mph)
and high loads
Proposed MethodDesign and construction of tribometerConduct experimentsDevelopment of the powder lubrication (CVFC) model
Predicts tribological parameters (e.g., friction and wear)
Film Transfer Experiments: Pellet-On Disk with Slider
•Higgs III, C.F., Ph.D Thesis, Rensselaer Polytechnic Institute, 2001
•Kaur, Higgs, and Heshmat, STLE Tribology Transactions, 2001
Measurables
1) Pad friction
2) Pellet friction
3) Pellet Wear
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
0 . 0 0 E + 0 0
5 . 0 0 E - 1 2
1 . 0 0 E - 1 1
1 . 5 0 E - 1 1
2 . 0 0 E - 1 1
2 . 5 0 E - 1 1
Wea
r Fa
ctor
,
S a m p le B
S a m p le C
0
0 . 0 5
0 . 1
0 . 1 5
Fri
ctio
n C
oeffi
cien
t, s
S a m p l e B
S a m p l e C
C o n t a c t P r e s s u r e , P c ( k P a )
1 0 2 0 . 1 4 9 . 6
1 0 2 0 . 1 4 9 . 6
C o n t a c t P r e s s u r e , P c ( k P a )
( a )
( b )
Contact Pressure Pc (psi)
Contact Pressure Pc (psi)
Past Powder Results: Friction and wear versus slider contact pressure
Dep
osit
ion
rate
(cm
3 cm
-1k
g-1)
Fri
ctio
n co
effi
cien
t
Proposed Research
Experimentation
Modeling
Pellet holder
Slider
Disk
Drive system
Experimentation: Pellet-On Disk with Slider Tribometer
Measurables:
1) Pad friction
2) Pellet friction
3) Pellet wear
Pellet holder
Slider
Disk
Drive system
Experimentation: Pellet-On Disk with Slider Tribometer(in construction)
Tribometer (Photograph)
(Boric acid powder )
Control Volume Fractional Coverage (CVFC) Model
XVFKXVKXVFkdt
dXhA
h
hVFK
h
hVFK
h
hVFk
dt
dhA
seseppp
sespeppp
)1(
)1(
max
maxmaxmax
RateOutput
FilmPowder -
RateInput
FilmPowder
Rate Storage
FilmPowder
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
TiC Disk
Lubricant Film
Journal Bearing
V
Pellet-on Disk:Deposits solid lubricant (by wearing)
Slider Pad
Slider Pad:Supports bearing load
MoS2 pellet
Fp
Fs
Wornyoh, E.Y.A., & Higgs, C.F., III, Proceedings of World Tribology Congress III, 2005
Conservation Law
Solving the CVFC Model
)exp(1
)()(
t
KKFKF
KFtX
peppess
pp
VKKFKF
Ah
peppess )(max
)( peppess
ppss KKFKF
KFX
Time Constant
Solution = Fractional Coverage
Steady State Fractional Coverage
Adopting the Linear Rule of Mixtures
pdrypp
sdryss
XX
XX
,lub,
,lub,
Dickrell, P.L., Sawyer, W.G., and Erdemir, A., Journal of Tribology, 2004
Pellet coefficient of friction
Slider coefficient of friction
Current and Proposed Research
Construction of tribometer
Pellet-on-disk with slider experiments
Powder lubrication modeling
Acknowledgements
The Dowd/ICES PhD fund at CMU
The Pennsylvania Infrastructure for Technological
Innovation (PITA)
Mechanical Engineering Machine Shop
Members of the Particle Flow & Tribology Laboratory
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