Transcript Document

2011 ASME Turbo Expo Congress & Exhibition
Parametric Study of Bump
Foil Gas Bearings for
Industrial Applications
GT2011-46767
Oscar De Santiago
CIATEQ A.C.
Queretaro, Qro, Mexico
http://rotorlab.tamu.edu
http://www.ciateq.mx/
Luis San Andres
Texas A&M University
College Station, TX, USA
1
Oil-Free Bearings for Turbomachinery
Justification
Current advancements in vehicle turbochargers and midsize
gas turbines need of proven gas bearing technology to
procure compact units with improved efficiency in an oil-free
environment. Also, Oil-free turbomachinery and subsea
compression are among major focuses in modern energy
industry.
DOE, DARPA, NASA interests range from applications as
portable fuel cells (< 60 kW) in microengines to midsize gas
turbines (< 250 kW) for distributed power and hybrid
vehicles.
Gas Bearings allow
• weight reduction, energy and complexity savings
• higher temperatures, without needs for cooling air
• improved overall engine efficiency
2
Available Bearing Technologies
Magnetic bearings
• Low to medium temperatures
• Moderate loads
• Need control systems
• Need back-up bearings
• Long history of operation in some
specific industrial applications
www.skf.com, 2011
www.synchrony.com, 2011
Schweitzer/Maslen 2009
•Current Magnetic Bearing solution is
expensive and even more expensive
(and difficult) to make it reliable
3
Available Bearing Technologies
Rolling element bearings • Low temperatures
• Low DN limit (< 2 M)
• Need lubrication system
Herringbone grooved bearing
NICH Center,
Tohoku University
AIAA 2004-4189
• Precision fabrication process
PowerMEMS 2003
• Low load capacity and stiffness
and little damping
Gas Foil Bearing
GAS BEARINGS
Flexure Pivot Bearing
• Oil-Free
• NO DN limit
• Low friction and power loss
• Thermal management
AIAA-2004-5720-984
4
GT 2004-53621
Microturbomachinery as per IGTI
Drivers:
deregulation in
distributed
power,
environmental
needs,
increased
reliability &
efficiency
Distributed power
(Hybrid Gas
turbine & Fuel Cell),
Hybrid vehicles
ASME Paper No. GT2002-30404
Honeywell, Hydrogen and Fuel Cells Merit
Review
Automotive
turbochargers,
turbo expanders,
compressors,
Max. Power ~
250 kWatt
5
International Gas Turbine Institute
Micro Gas Turbines
Microturbine Power Conversion Technology Review, ORNL/TM-2003/74.
Cogeneration systems with high efficiency
• Multiple fuels (best if
free)
• 99.99X% Reliability
• Low emissions
• Reduced maintenance
• Lower lifecycle cost
60kW MGT
MANUFACTURER
OUTPUT POWER (kW)
Bowman
25, 80
Capstone
30, 60, 200
Elliott Energy
Systems
35, 60, 80, 150
General
Electric
175
Ingersoll
Rand
70, 250
Turbec, ABB &
Volvo
100
Hybrid System : MGT with
Fuel Cell can reach efficiency
> 60%
www.microturbine.com
Ideal to replace reciprocating
engines. Low footprint desirable
6
Examples of commercial applications
Micro Turbines
•Capstone of California
7
Turbo chargers
•Honeywell “on the race”
Examples of commercial applications
Industrial Air Compressors
•Samsung’s successful Micro Turbo
Master line of compressors feature
gas foil bearings
•Pressures up to 130 psig
•Powers up to 0.13 MW
•Samsung has another line (Turbo
Master) of air compressors with
pressures up to 300 psig and
power up to 2.4 MW (~20x larger).
Run on TPJB.
What’s next ??
8
www.samsungtechwin.com, 2011
MTM – Needs, Hurdles & Issues
Largest power to weight
ratio,
Compact & low # of parts
High energy density
Reliability and efficiency,
Low maintenance
High speed
Rotordynamics &
(Oil-free) Bearings & Sealing
Materials
Coatings: surface conditioning for
low friction and wear
Ceramic rotors and components
Manufacturing
Extreme temperature and
pressure
Automated agile processes
Cost & number
Processes & Cycles
Environmentally safe (low
emissions)
Lower lifecycle cost ($ kW)
Low-NOx combustors for liquid &
gas fuels
TH scaling (low Reynolds #)
Fuels
Best if free (bio-fuels)
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Gas Bearings for Oil-Free MTM
Advantages of gas bearings over oil-lubricated
bearings
– Process gas is cleaner and eliminates
contamination by buffer lubricants
– Gases are more stable at extreme temperatures
and speeds (no lubricant vaporization,
cavitation, solidification, or decomposition)
– Gas bearing systems are lower in cost: less
power usage and small friction, enabling
savings in weight and piping
Gas Bearings Must Be Simple!
10
Ideal gas bearings for MTM
Load Tolerant – capable of handling both normal and
extreme bearing loads without compromising the integrity of the
rotor system.
Simple – low cost, small geometry, low part count, constructed
from common materials, manufactured with elementary methods.
High Rotor Speeds – no specific speed limit (such as DN)
restricting shaft sizes. Small Power losses.
Good Dynamic Properties – predictable and repeatable
stiffness and damping over a wide temperature range.
Reliable – capable of operation without significant wear or
required maintenance, able to tolerate extended storage and
handling without performance degradation.
+++ Modeling/Analysis
(anchored to test data) available
11
Gas Bearings for MTM
What are the needs?
Make READY technology for industrial
application by PUSHING development to
• make out of the shelf item with proven
results for a wide range of applications;
• engineered product with well known
manufacturing process;
• known (verifiable) performance with solid
laboratory and field experiences
12
Gas Bearings Research at TAMU
See References at end
Thrust:
Investigate conventional bearings of low cost, easy
to manufacture (common materials) and easy to
install & align.
Combine hybrid (hydrostatic/hydrodynamic)
bearings with low cost coating to allow for rub-free
operation at start up and shut down
Major issues: Little damping, Wear at start & stop,
Nonlinear behavior (subsync. whirl)
13
Gas Bearing Research at TAMU
2001/2 - Three Lobe Bearings
Stability depends on feed pressure.
Stable to 80 krpm with 5 bar pressure
2003/4 - Rayleigh Step Bearings
Worst performance to date with grooved bearings
Flexure pivot tilting pad –
hybrid gas bearing.
2002-09 - Flexure Pivot Tilting Pad Bearings
Stable to 93 krpm w/o feed pressure.
Operation to 100 krpm w/o problems. Easy to
install and align.
2004-11: Bump-type Foil Bearings
Industry standard. Reliable but costly.
Models anchored to test data.
2008-12: Metal Mesh Foil Bearings
Cheap technology. Still infant. Users needed
See References at end
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Gas Foil Bearings
15
Gas Foil Bearings
Ө
Top foil spot weld
Top foil
Bump strip layer
Ω
Y
Rotor
spinning
Gas film
Housing
X
: Bump spot weld
Advertised advantages: high load capacity (>20 psig),
rotordynamically stable, tolerance of misalignment and
shocks
16
Gas Foil Bearings – Bump type
• Series of corrugated foil structures (bumps)
assembled within a bearing sleeve.
• Integrate a hydrodynamic gas film in series
with one or more structural layers.
Applications: APUs, ACMs, micro
gas turbines, turbo expanders
• Reliable
• Tolerant to misalignment and
debris, also high temperature
• Need coatings to reduce friction at
start-up & shutdown
• Damping from dry-friction and
operation with limit cycles
17
Foil Bearings (+/-)
•
•
•
•
•
Increased reliability: load capacity (< 20 psi)
No lubricant supply system, i.e. reduce weight
High and low temperature capability (> 1,000 C)
No scheduled maintenance
Tolerate high vibration and shock load. Quiet
operation
• Endurance: performance at start up & shut down
(lift off speed)
• Little test data for rotordynamic force coefficients &
operation with limit cycles (sub harmonic motions)
• Thermal management for high temperature
applications (gas turbines, turbochargers)
• Predictive models lack validation for GFB operation
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at HIGH TEMPERATURE
Computational
analysis
19
Theoretical basis
• Solve Reynolds equation for compressible flow
(isothermal case).
• Coupled to bump metal sheet deformation (nonlinear stiffness and damping).
• Iterative solution to find bearing equilibrium
position.
• Perturbation analysis to find dynamic performance
(frequency-dependent stiffness and damping
coefficients).
Refs: San Andrés (2009), Arghir (2004), Iordanoff (1999), Heshmat (1992)
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The computational program
• Windows OS and MS Excel 2003 (minimum requirements)
• Fortran 99 Executables for FE underspring
structure and gas film analyses. Prediction of
forced – static & dynamic- performance.
• Excel® Graphical User Interface (US and SI
physical units). Input & output (graphical)
• Compatible with XLTRC2 and XLROTOR codes
Code: XL_GFBTHD
21
Graphical User Interface
Worksheet: Shaft & Bearing models (I)
22
Graphical User Interface
Worksheet: Shaft & Bearing models (II)
23
Graphical User Interface
Box 8
Box 9
Box 10
Worksheet: Top Foil and Bump Models
24
Graphical User Interface
Worksheet: Foil Bearing (Operation and Results)
25
Parametric Study
Ө
Top foil spot weld
Top foil
Bump strip layer
Ω
Y
Rotor
spinning
Gas film
Housing
X
: Bump spot weld
26
Results
• Example bearing (Ref [3]):
1.0E+13
Original bump geometry
Bump foil thickness, tb
Bump pitch, s0
Bump half length, l0
Bump height, hb
Foil Elastic modulus, E
Foil Poisson's ratio, ν
Friction Coefficient, μf
0.0349
0.0445
1.28
7.62E-05
3.18E-03
1.27E-03
5.10E-04
214.00
0.29
0
meters
meters
meters
meters
meters
meters
GPa
Original bump stiffness/area 1.65E+10 N/m3
1.0E+11
1.0E+10
1.0E+09
1.0E+08
0.0E+0
1.0E-4
2.0E-4
3.0E-4
4.0E-4
5.0E-4
Bump foil thickness (m)
2.50E+10
Unit stiffness (N/m3)
Bearing diameter:
Bearing axial length:
L/D=
Unit stiffness (N/m3)
1.0E+12
2.00E+10
1.50E+10
1.00E+10
5.00E+09
0.00E+00
0.002
0.003
0.004
0.005
Bump pitch (m)
• Bump unit area stiffness lowers as bump pitch
increases
• Bump unit area stiffness increases with foil
thickness
0.006
27
Results
Measured load capacity (Ref [3])
2.4
Current predictions, constant
load of 31 psi
31 psi
With Cu
2.2
Minimum Film Thickness
6.0
Calibration point 1
2
Film Thickness (microns)
1.8
Bearing Load Capacity (Bar)
1.6
1.4
1.2
No Cu
1
0.8
5.0
4.0
Minimum film
3.0
Calibration point 2
2.0
0.6
1.0
0.4
0.2
0.0
0
0
0
20
40
60
80
100
120
140
20,000
40,000
60,000
80,000
100,000
120,000
140,000
Rotor Speed (RPM)
Rotor Speed (k rpm)
• Benchmarking with independent experiments –
Generation 1 bearing (Ref [3]).
• Used to find practical limit of film thickness
28
Results
Operating eccentricity
Displacement (microns)
Displacement (microns)
Operating eccentricity
150.00
120.00
90.00
60.00
30.00
0.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0
1.0E+08
1.0E+09
1.0E+10
1.0E+11
Bump unit stiffness (N/m3)
Eccentricity
100
1.0E+12
200
300
400
Unit Load (kPa)
Eccentricity
Min film thickness
Min film thickness
• Base bearing (Ref [3]):
Bearing diameter:
Bearing axial length:
L/D=
Displacement (microns)
Operating eccentricity
50.00
0.0349
0.0445
1.28
meters
meters
7.62E-05
3.18E-03
1.27E-03
5.10E-04
214.00
0.29
0
meters
meters
meters
meters
GPa
40.00
30.00
20.00
10.00
0.00
0
0.5
1
1.5
L/D (-)
Eccentricity
Min film thickness
2
2.5
Original bump geometry
Bump foil thickness, tb
Bump pitch, s0
Bump half length, l0
Bump height, hb
Foil Elastic modulus, E
Foil Poisson's ratio, ν
Friction Coefficient, μf
29
Original bump stiffness/area 1.65E+10 N/m3
Rule of thumb for design
Minimum Film Thickness
• Bearing scaling: use
Della Corte´s rule:
W ~ N L D^2
• Bump scaling:
Knew = Korig / f ;
f is de diameter scale
factor
5.0
4.0
Minimum film
3.0
2.0
1.0
0.0
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
Rotor Speed (RPM)
1.0E+13
1.0E+12
Unit stiffness (N/m3)
From observations of bump
stiffness and bearing
performance predictions:
Film Thickness (microns)
6.0
1.0E+11
1.0E+10
1.0E+09
1.0E+08
0.0E+0
1.0E-4
2.0E-4
3.0E-4
4.0E-4
Bump foil thickness (m)
5.0E-4
30
Application example
• Industrial compressor for
injection service
• 8 impellers, 640 lb rotor
Bearing characteristics
Rotor Diameter, D
Length, L
Radial
clearance,
c
*
Load, W
W/LD
132 mm (5.21 in)
169 mm (6.64 in)
96 µm (3.8 mil)
1,421 N (319 lb)
0.636 bar (9.21 psi)
• Re-configured rotor – move
bearings INBOARD of gas seals
• Use larger diameter at bearing
location
Expected speed range:
3 to 20 krpm
13-15 krpm MCOS most typical
31
Application - rotordynamics
Linear stability analysis
Undamped Critical Speed Map
Example rotor on Foil Bearings
Critical Speed, cpm
100000000
10000000
1000000
100000
10000
1000
100
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E+07
Bearing Stiffness, lbf/in
Predicted stiffness range
Damped Eigenvalue Mode Shape Plot
Example compressor on Foil Bearings
forward
backward
st
f=7556.7 cpm
d=17.0342 qfac
N=7557 rpm
5th
Mode Frequency Log dec AF
Comments
(cpm)
st
2600
1.306 2.5 Forward,
1
horizontal,
cylindrical
nd
2906
1.494 2.2 Forward,
2
horizontal,
conical
rd
5333
0.837 3.8 Forward,
3
vertical, flexible
(DE overhung)
th
5556
0.677 4.7 Forward,
4
vertical, flexible
(DE overhung)
th
7557
0.185 17 For/backward,
5
horizontal, 1st
rotor flexible
th
8503
0.676 4.7 Forward,
6
Compressor
can´t cross
these
speeds
(requires
more
damping)
7th
17,554
0.054
th
18,580
0.045
8
vertical,
1
rotor flexible
58 Backward,
vertical/horizon
tal, 2nd flexible
70 Forward,
vertical/horizon
tal, 2nd flexible
32
Observations
– Conceptually, scaled gas foil bearings can support an
industrial, flexible rotor.
– Re-location of bearings is necessary to decrease unit
load, but it is feasible in the compressor working
environment.
– Rotor-bearing system requires additional damping to
control shaft vibration at critical speeds.
Rotordynam ic Response Plot
Example Compressor on Foil Bearings
Sta. No. 10: M idspan
2
1.6
Example Compressor on Foil Bearings
30
1.4
M ajor Amp
1.2
20
Horz Amp
1
Vert Amp
0.8
Excitation = 1x
0.6
0.4
0.2
Shaft Radius, inches
Response, mils pk-pk
1.8
10
Shaft1
1
5
10
Shaft1
18
15
0
-10
-20
0
-30
0
5000
10000
Rotor Speed, rpm
15000
20000
0
20
40
60
Axial Location, inches
80
100
33
Closure
Dominant challenges for gas bearing technology:
– Low gas viscosity requires minute clearances to
generate load capacity.
– Damping & rotor stability are crucial
– Inexpensive coatings to reduce drag and wear
– Bearing design & manufacturing process well
known
– Adequate thermal management to extend
operating envelope into high temperatures
34
Closure
Other pressing challenges for gas bearing
technology:
intermittent contact and damaging wear at
startup & shut down, and
temporary rubs during normal operating
conditions
Current research focuses on
coatings (materials),
rotordynamics (stability) & high
temperature (thermal
management)
Need Low
Cost &
Long Life
Solution!
35
Oil-Free Bearings for Turbomachinery
References
36
References Foil Bearings
ASME GT2011-46767
De Santiago, O., and San Andrés, L., 2011, “Parametric Study of Bump Foil Gas
Bearings for Industrial Applications”
ASME GT2011-45763
San Andrés, L.., and Ryu, K., 2011, “On the Nonlinear Dynamics of Rotor-Foil Bearing
Systems: Effects of Shaft Acceleration, Mass Imbalance and Bearing Mechanical Energy
Dissipation.”
ASME GT2010-22508
Howard, S., and San Andrés, L., 2011, “A New Analysis Tool Assessment for
Rotordynamic Modeling of Gas Foil Bearings,” ASME J. Eng. Gas Turbines and Power,
v133
NASA/TM 2010-216354
ASME GT2010-22981
San Andrés, L., Ryu, K., and Kim, T-H, 2011, “Thermal Management and Rotordynamic
Performance of a Hot Rotor-Gas Foil Bearings System. Part 2: Predictions versus Test
Data,” ASME J. Eng. Gas Turbines and Power, v133
ASME GT2010-22981
San Andrés, L., Ryu, K., and Kim, T-H, 2011, “Thermal Management and Rotordynamic
Performance of a Hot Rotor-Gas Foil Bearings System. Part 1: Measurements,” ASME J.
Eng. Gas Turbines and Power, v133
8th IFToMM Int. Conf.
on Rotordynamics
San Andrés, L., Camero, J., Muller, S., Chirathadam, T., and Ryu, K., 2010,
“Measurements of Drag Torque, Lift Off Speed, and Structural Parameters in a 1st
Generation Floating Gas Foil Bearing,” Seoul, S. Korea (Sept.)
ASME GT2009-59920
San Andrés, L., Kim, T.H., Ryu, K., Chirathadam, T. A., Hagen, K., Martinez, A., Rice, B.,
Niedbalski, N., Hung, W., and Johnson, M., 2009, “Gas Bearing Technology for Oil-Free
Microturbomachinery – Research Experience for Undergraduate (REU) Program at
Texas A&M University
AHS 2009 paper
Kim, T. H., and San Andrés, L., 2010, “Thermohydrodynamic Model Predictions and
Performance Measurements of Bump-Type Foil Bearing for Oil-Free Turboshaft Engines
37
in Rotorcraft Propulsion Systems,” ASME J. of Tribology, v132
References
Foil Bearings
ASME GT2009-59919
San Andrés, L., and Kim, T.H., 2010, “Thermohydrodynamic Analysis of Bump Type gas
Foil Bearings: A Model Anchored to Test Data,” ASME J. Eng. Gas Turbines and Power,
v132
IJTC2008-71195
Kim, T.H., and San Andrés, L., 2009, "Effects of a Mechanical Preload on the Dynamic
Force Response of Gas Foil Bearings - Measurements and Model Predictions," Tribology
Transactions, v52
ASME GT2008-50571
IJTC2007-44047
Kim, T. H., and San Andrés, L., 2009, “Effect of Side End Pressurization on the Dynamic
Performance of Gas Foil Bearings – A Model Anchored to Test Data,” ASME J. Eng. Gas
Turbines and Power, v131. 2008 Best PAPER Rotordynamics IGTI
ASME GT2007-27249
San Andrés, L., and Kim, T.H., 2009, “Analysis of Gas Foil Bearings Integrating FE Top
Foil Models,” Tribology International, v42
AIAA-2007-5094
San Andrés, L., and T.H. Kim, 2007, “Issues on Instability and Force Nonlinearity in Gas
Foil Bearing Supported Rotors,” 43rd AIAA/ASME/SAE/ASEE Joint Propulsion
Conference, Cincinnati, OH, July 9-11
ASME GT2005-68486
Kim, T.H., and L. San Andrés, 2008, “Heavily Loaded Gas Foil Bearings: a Model
Anchored to Test Data,” ASME J. Eng. Gas Turbines and Power, v130
ASME GT2006-91238
San Andrés, L., D. Rubio, and T.H. Kim, 2007, “Rotordynamic Performance of a Rotor
Supported on Bump Type Foil Gas Bearings: Experiments and Predictions,” ASME J.
Eng. Gas Turbines and Power, v129
ASME GT2004-53611
San Andrés, L., and D. Rubio, 2006, “Bump-Type Foil bearing Structural Stiffness:
Experiments and Predictions,” ASME J. Eng. Gas Turbines and Power, v128
38
References
Metal mesh foil bearings
ASME GT2011-45274
San Andrés, L., and Chirathadam, T., 2011, “Metal Mesh Foil Bearings: Effect of
Excitation Frequency on Rotordynamic Force Coefficients
ASME GT2010-22440
San Andrés, L., and Chirathadam T.A., 2010, “Identification of Rotordynamic Force
Coefficients of a Metal Mesh Foil Bearing Using Impact Load Excitations.”
ASME GT2009-59315
San Andrés, L., Chirathadam, T. A., and Kim, T.H., 2009, “Measurements of Structural
Stiffness and Damping Coefficients in a Metal Mesh Foil Bearing.”
AHS Paper
San Andrés, L., Kim, T.H., Chirathadam, T.A., and Ryu, K., 2009, “Measurements of
Drag Torque, Lift-Off Journal Speed and Temperature in a Metal Mesh Foil Bearing,”
American Helicopter Society 65th Annual Forum, Grapevine, Texas, May 27-29
Other
ASME DETC200734136
Gjika, K., C. Groves, L. San Andrés, and G. LaRue, 2007, “Nonlinear Dynamic
Behavior of Turbocharger Rotor-Bearing Systems with Hydrodynamic Oil Film and
Squeeze Film Damper in Series: Prediction and Experiment.”
39
CIATEQ´s full-size rotordynamic rig
40
Acknowledgments
Thanks to
NSF (Grant # 0322925)
NASA GRC (Program NNH06ZEA001N-SSRW2),
Capstone Turbines, Inc.,
Honeywell Turbocharging Systems,
Korea Institute of Science and Technology (Dr. TaeHo Kim)
Foster-Miller, MiTI,
TAMU Turbomachinery Research Consortium (TRC)
CIATEQ A.C.
Learn more:
http://rotorlab.tamu.edu
41