Transcript Identification of Stiffness and Damping Coefficients in a

ASME
Turbo Expo
2009:Brush
Power
for Force
Land, Coefficients
Sea, and Air
GT2009-59072
Hybrid
Seal
ROTORDYNAMIC FORCE COEFFICIENTS OF A
HYBRID BRUSH SEAL:
MEASUREMENTS AND PREDICTIONS
Luis San Andres
Jose Baker
Mast-Childs Professor
Texas A&M University
Project Engineer
KBR, Inc.
Adolfo Delgado
Mechanical Engineer
GE Global Research Center
ASME GT2009-59175
accepted for journal publication
Supported by Siemens Power Generation
GT2009-59072 Hybrid Brush Seal Force Coefficients
Trends in High Performance Turbomachinery:
- Higher speeds
- Extreme operating temperatures and pressures
Issues of Importance
- Increase in secondary flows (parasitic leakage)
- Increase in specific fuel consumption and COST
- Reduction in power delivery
- Potential for rotordynamic instability
Improved Brush Seal Technology Offers:
Higher engine performance with less parasitic leakage
Improved engine stability and reduced engine vibration
Lower operating and maintenance costs
Justification
GT2009-59072 Hybrid Brush Seal Force Coefficients
Hybridseals
Brush
(HBS) Seals
Brush
vs.Seal
Labyrinth
Advantages
Advantages
•Handle
amplitudes
vibration SBS
• All thelarge
advantages
of 1stofgeneration
•Less
axial space
• Reduced
leakage (~36%) over 1st
generation
shoed brush
seal (90%)
•Reduced
secondary
flow leakage
• Pads connected via EDM-webs, no
Disadvantages
spot welds between pads and bristles
•Pressure differential limitation
• Higher axial stiffness, prevents pad
•Wear
and local
thermal
distortion
motions
at high
pressure
differentials
Shoed Brush Seal (SBS)
Advantages
• Incorporates metal shoes
at the free end of the bristle
– Reduces and eliminates wear
“shoes lift off”
• Bi-directional shaft rotations
Disadvantages
•
Pads “roll over” under high
pressure differential
GT2009-59072 Hybrid Brush Seal Force Coefficients
LITERATURE REVIEW: Hybrid Brush Seals
•Chupp et al. (2006): comprehensive review on sealing
technology, including brush seals and shoed brush seals.
• Justak
introduces a film riding seal
with hydrodynamic pad action.
(U.S. Patent 7,182,345)
• Delgado and San Andrès
(Sealing Technology, 2005)
measure leakage and structural characteristics of a shoedbrush seal.
• San Andrès et al. (ASME GT2008-50532 ) measure leakage
and power loss in a Hybrid Brush Seal built with
interference. HBS has approximately 36% less leakage then
a shoed brush seal.
• San Andrès & Ashton (2009 STLE Meeting) compare leakage
performance of three seals at high temperature
GT2009-59072 Hybrid Brush Seal Force Coefficients
Experimental Facility
Supply pressure
inlet
Supporting
springs
Rotor
Structural parameters
Kshaft= 243 lbf/in (42.5 kN/m)
Ms+d= 9.8 lb (4.45 kg)
Electromagnetic
Shaker
Stinger
z: 0.01 % (damping ratio)
Eddy current
sensosrs
Installation:
Pressure
Vessel
DC Motor
Flexible
coupling
Quill shaft
cm 10
6.550” diameter brush seal
Max. air Pressure: 60 psig
Shaker (20 lb max)
High pressure air
20
30
40
Eddy current
sensor
50
60
70
80
Roller
bearing
assembly
90 100
Flow
Disk
Seal
Ps
Ball bearing
Pe
Shaft
Flow
Flow
Disc
Spring
Detail of brush seal test rig
Flexible
coupling to
motor
Hybrid brush
seal
GT2009-59072 Hybrid Brush Seal Force Coefficients
Physical Properties
Rotor diameter, Dj
Brush seal (pads) inner diameter, Dsi
Brush seal (retainer) outer diameter, Do
Brush seal width, Bw
Radial Interference between rotor and seal, Ri
Number of pads
Width of pads
Bristle lay angle, α
Bristle modulus of elasticity, E
Bristle density (circumference)
SI unit
167.1 mm
166.4 mm
183.1 mm
8.53 mm
0.381 mm
20
7.23 mm
45 deg.
5
22.48x10 bar
850 bristle/cm
English Unit
6.580 in
6.550 in
7.210 in
0.336 in
0.015 in
0.331 in
6
32.6x10 psi
2200 bristle/ in
B ristle B ed
B a ck P late
P ad o r sho e
* Close-up courtesy of Advanced
Technologies Group, Inc.
H ig h P ressure Sid e
Spring Lever
Mechanism
L o w P ressure Sid e
Seal
Courtesy of Advanced Technologies Group®
Ps
Pe
Flow
*: C lo se-u p co u rtesy o f A d v an ced Tech n o lo g ies G ro u p , In c.
Sp ring -L ev er
M ech a nism
Test Hybrid Brush Seal (HBS)
Disc
GT2009-59072 Hybrid Brush Seal Force Coefficients
Identification of Rotordynamic Force Coefficients
Electromagnetic
Shaker
Kyy, Cyy
Eddy current
sensors
Kyx, Cyx
Load Cell
Y
Y
Kxx, Cxx
X
X
Disk
Ω
Stinger
HBS
Kxy, Cxy
For rotor
M xy   x  operation:
 M xx centered
 K xx K xy   x   C xx C xy   x   F x   Fix 
K xy  x  C xx  0   x   F x   Fix 
0   x    K xx
 M xx
M yx M yy  y   K yx K yy   y C yx C yy   y    0   Fiy   


K
K
F
0
M
0
C

xx
  y

xy
xx
  y

xx
  y
 0 

iy

GT2009-59072 Hybrid Brush Seal Force Coefficients
Identification of HBS rotordynamic force Coefficients
Identification at excitation frequency (ω) ≠ rotor speed (Ω)
Z xx  x  Z xy  y  F x
System Impedances
Z yx  x  Z yy  y  0
Z   K   M  
Z xx  Z yy
and
Impedance Function
2
 iC   ,   x , y
Z xy   Z yx
Effect of rotor speed on rotor-HBS natural frequency
Location of
displacement
measurements
0.1
[m]
Shaft
ShaftRadius
Radius, [m]
Shaft
Radius,
[m]
0
GT2009-59072 Hybrid Brush Seal Force Coefficients
0
0.05
Gyroscopic
effects negligible
for test rotor
speeds
(600 and 1,200
rpm [20 Hz])
Disk
0.075
Roller bearing
support
Shaft
0.025
0
-0.025
Location of
external force
-0.05
Hybrid Brush
Seal location
-0.075
-0.1
0.05
0
0.1
0.05
0.15
0.1
0.2
0.15
0.25
0.2
0.3
0.25
0.35
0.3
0.35
Axial Location, [m]
Axial
Location,
z [m]
Axial Location,
[m]
Axial Location,
[m]
Rotor
Speed [RPM]
1st Backward Nat.
Frequency, [Hz]
1st Forward Nat.
Frequency, [Hz]
2nd Forward Nat.
Frequency, [Hz]
3rd
0
30.5
30.5
146
1351
600
29.7
31.4
154
1351
1200
28.8
32.2
163
1351
Forward Nat.
Frequency, [Hz]
GT2009-59072 Hybrid Brush Seal Force Coefficients
Cross coupling effects under rotation
X - D isp la ce m e n t [u m ]
[m]
X-displacement
1000
X
32 Hz
750
For load along X
Synchronous with speed (1X)
direction,
rotor (X) motions
22 N
Due to excitation
500
>>>
250
0
Load=22 N
600 rpm
40
40
120
200
280
360
cross (Y) motions
440
Frequency [Hz]
Frequency
[Hz]
Y - D isp la ce m e n t [u m ]
[m]
Y-displacement
1000
Y
1X motions
always small
compared to
excitation
22 N
750
Synchronous with speed (1X)
32 Hz
Due to excitation
500
250
0
40
40
120
200
Frequency [Hz] [Hz]
Frequency
280
360
440
5  10 5
5  10
 10 5
5
GT2009-59072
Hybrid Brush Seal Force Coefficients
5
5 5 5
 10
 10
5  10 5 5
5
10
5
5
5  10
5  10
5
5  10
0
0
Z xx 
0
Load = 22 N,0frequency
25-80Hz
000
0
0
5

5 10
0
5

5 10 5
Kxx - 22Mxx
5
5  10

5 10
xx
xx
5
5 5 5

 10
 10
5 10 5 5
5
10
5
5
5  10
5  10
0
 10 5
5
6
TESTs
1  10
6
0 6
20
40
60
80
100
1  10
1
10
Model
0 6 6 6 0 20
40
60
6
20 Frequency
40
60 80
80 100
 10
 10
 10
[Hz]
1  10 1 1
1
0
40
6
202020
4040
4060
60606080
808080100
0 0 20
Frequency
[Hz]
 10 6 0 Test
Frequency
[Hz]
Test
Data
1  10
1
Model
Data
5
0
20
40
0Test
20 Frequency
40
60 80
80 100
6
[Hz]60 [Hz]
Frequency
[Hz]
5  10
[Hz]
600
rpm,
= Frequency
1.7
ModelData
Test
DataPr Frequency
1  10
0Model
20
40
80
Frequency
[Hz]
[Hz]60
Test Data
Test
Data
Test
Test
Data
Data
1200
rpm,
Pr = Frequency
1.7
R e(Z xx1 ) [N /m ]
R e(Z
R) e(Z
xx1
xx1
) /m
[N
[N ]/m ]
R e(Z
xx1
[N
R e(Z
xx1
)]/m
[N)]/m
R e(Z xx1 ) [N /m ]
R e(Z
R e(Z
R
xx1
xx1
xx1
)/m
)]/m
) ][N
[N
[N
/m/m
] ]
R e(Z
xx1
) e(Z
[N
R e (Z
xx1 ) [N[kN/m]
/m ]
(Zxx)
Re
Dynamic Stiffness vs. Frequency
K
 M
Model
600
rpm,
2.4
[Hz]
Test Data
Model
Test
DataPr = Frequency
Model
Model
Model
Model 1200
Testrpm,
DataPr = 2.4
Model
6
1  10

20
40
60
Frequency [Hz]
Frequency
[Hz]
Test Data
80
(x  y )
2
2
Model
reproduces
the measured
real part of
100
impedance.
100
100
100
100
Little effect
of
100
pressurization
Model
0
Fx  x
100
4  10
4  10
4
4
GT2009-59072 Hybrid Brush Seal4 Force
Coefficients
10
4
4
4  10
4
4  10
 4
4
4  10
 4
2 10 4
4  10 4
2  10
2 10 4
4  10 4
2  10
R/X
R
e(F
(F
/X/m
)/X[N
[N ]/m ]
R e(FR/Xe)(F[N
/m)e][N
]) /m
R/X
R
e(F
(F
/X/m
)/X[N
[N ]/m ]
R e(FR/Xe)(F[N
/m)e][N
]) /m
Cross-coupled Stiffness vs. Frequency
4
2  10
Load =2 10220 N, frequency 20-80Hz
4
0
0 Pr = 1.7, Zxy =- Zyx
2  10 4 0
2 410

2 10
4
2  10
1200 rpm
4
4
2  10 4
 10 4
4
0
4 10
2  10
Pressure ratio
4
4  10
4

2 10
20
20
0
20
40
40
60
60
600 rpm
600
60
Frequency
Frequency [Hz]
[Hz]
40
Zxy=-Zyx (Test
Data)
Frequency
0
20
40 [Hz]
Zxy=-Zyx
(Model)
Zxy=-Zyx
Data)
Test
Data (Test
Frequency
[Hz]
Stiffness
[kN/m],
Kxy
Zxy=Zyx (Test
Data)
Zxy=-Zyx
(Model)
Zxy=-Zyx (Test Data)
Zxy=Zyx (Test
(Model)
Model
Zxy=Zyx
Data)
Zxy=-Zyx (Model)
Mass [kg.],
M (Model)
Zxy=Zyx
Zxy=Zyxxy
(Test Data)
4
4  10
0
20
4
Pr=1.7
Rotor Speed [rpm], Ω
4
4  10
0
0
4
2  10 0
0
4
4  10
R e (Z xy) [N /m ]
R e (Z xy) [N /m ]
4
4  10
4
2  10
40
Zxy=Zyx
(Model)
Frequency [Hz]
Zxy=-Zyx (Test Data)
Zxy=-Zyx (Model)
80
60
80
8.8
60
80
80
0
80
0
Pr = 2.4, Zxy =- Zyx
4
2  10 4 0
2  10
Pr=2.4
4
2  10 4
 10 4
4
4  10
4
4  10
1200
4  10
0
0
0
4
4
15
4
4  10
1200 rpm
4
2  10
0
2  10
Z xy   Z yx  Z xx
00
0
20
20
40
40
60
60
80
80
Frequency [Hz]
Frequency
20
40 [Hz]
60
600
1200
rpm
Zxy=-Zyx
(Test Data)
Data)600
Zxy=-Zyx
(Test
20
Frequency
40 [Hz]
Zxy=-Zyx (Test
(Model)
Zxy=-Zyx
Data)
Test
Data Frequency
[Hz]
Zxy=Zyx
(Test
Data)
Zxy=-Zyx
(Model)
Zxy=-Zyx (Test Data)
Zxy=Zyx (Model)
Model
Zxy=Zyx
Data)
Zxy=-Zyx(Test
(Model)
Zxy=Zyx
Zxy=Zyx (Model)
(Test Data)
20 Zxy=Zyx (Model)
40
60
80
60
2.7
6.6
0
0
80
80
Frequency [Hz]
Zxy=-Zyx (Test Data)
Zxy=-Zyx (Model)
•Identified cross-coupled mass is nearly 0 kg.
•Identified cross-coupled stiffness (Kxx = -Kyx) is estimated
as a constant independent of excitation frequency.
•Kxy doubles as rotor speed increases from 600 and 1,200
rpm for both pressure conditions
y
x
GT2009-59072 Hybrid Brush Seal Force Coefficients
Equivalent Viscous Damping (Cxx~Ceq) vs.
Frequency
600 rpm
Damping
decreases with
frequency, with
little effect of
supply
pressure.
Minimum value
at test system
natural
frequency (~32
Hz)
1200 rpm
Pr=1.7
Pr=2.4
Supply Pressure/Exhaust Pressure
GT2009-59072 Hybrid Brush Seal Force Coefficients
Force coefficiensts: system & seal
Load = 22 N, frequency 25-80Hz
No rotation
Tests with rotor spinning
Pr = 1.0
Pressure ratio
Rotor Speed [rpm], Ω
Pr=1.7
Pr=2.4
0
600
1200
600
1200
120
108
98
130
124
Mass [kg.], Mxx
2.11
2.62
2.54
2.43
2.39
R2 (correlation factor)
Dynamic stiffness
(Kxx – Mxxω2)
0.97
0.98
0.98
0.98
0.98
103
89
135
128
0.39
0.36
0.37
0.38
0.29
0.26
0.33
0.34
Stiffness [kN/m],
Kxx
HBS stiffness[kN/m],
HBS Dry Friction
coefficient, μ
HBS Loss Factor
coefficient, 
Ks
93
0.66
0.42
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS predicted stiffness vs. frequency
Frequency 25-100 Hz
Stiffness
Coefficients [kN/m]
[kN/m]
Coefficients
Stiffness
Stiffness Coefficients [kN/m]
140
140
rpm
Ksxx 600
= Ksyy,
Pr = 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
HBS =
Measured
Ks
Ksxx
Ksyy, Pr Stiffness,
= 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
130
140
130
Stiffness Coefficients [kN/m]
120
120
130
110
110
120
100
100
110
Ksxx = Ksyy, Pr = 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
Ksxx
= Ksyy,
1,200
rpmPr = 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
9090
100
808090
7070
80
HBS Measured Stiffness, Ks
HBS Equivalent Stiffness, Ks
6060
70
00
2020
4040
6060
HBS Equivalent Stiffness, Ks
8080
120
120
Frequency[Hz]
[Hz]
Frequency
60
0
Equivalent Stiffness, Ks
Frequency
[Hz]
20
40
60
80
Frequency
[Hz]
HBS Equivalent
Stiffness,
Ks
Code: XLTPGASBEAR®
20
100
100
Predicted HBS
stiffness (Ksxx)
drops slightly in
range from 20100 Hz.
Tests show nearly
constant Ksxx
40
60
80
ASME
GT2004-53614
Frequency [Hz]
100
120
100
120
Pressure (Pr = Ps/Pd) has
negligible effect on seal direct
stiffness, Ksxx
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS viscous damping coeff. vs. frequency
Frequency 25-100 Hz
1 11
0.9
0.40.4
0.4
0.30.3
0.3
0.20.2
0.2
0.10.1
0.1
Damping Coefficients [kN-s/m]
0.60.6
0.6
0.8
0.7
0.6
Increasing loss factor ( 
0.5
0.2
0.1
0.4
0 00
0.3
0 00
20 20
20
0.2
0
40 40
40
60 60
60
80 80
80
100100
100
100
1,200 rpm
Cxx = Cyy,  = 0.25
Cxx = Cyy,  = 0.55
Equivalent Viscous Damping, Ceq
Cxx = Cyy, = 0.25
1200 rpm
Cxx = Cyy, = 0.55
Equivalent Viscous Damping, Ceq
IncreasingCxx
loss
factor= (0.25
)
= Cyy,
IncreasingIncreasing
loss factorloss
(  factor
Cxx
=PrCyy,
=
0.55

=(2.4
Equivalent Viscous Damping, Ceq
Cxx = Cyy,  = 0.25
Cxx = Cyy,  = 0.55
Equivalent Viscous Damping, Ceq
0.9
0.9
0.9
0.8
0.8
0.8
rpm
0.7
0.7
0.7 1
0.6
0.6
0.60.9
0.5
0.5
0.50.8
0.4
0.4
0.40.7
0.3
0.3
0.30.6
Increasing loss factor ( 
0.2
0.2
0.20.5
0.1
0.1
0.10.4
0000.3
0
000 20
120120
1200.2
120
Frequency
[Hz]
Frequency
[Hz]
Frequency
[Hz]
0.1
1200 rpm
1200
rpm
1200
1200rpm
rpm
Pr = 1.7
Coefficients [kN-s/m]
[kN-s/m]
Damping Coefficients
Coefficients
[kN-s/m]
Damping
Damping Coefficients [kN-s/m]
Damping
Damping Coefficients
Coefficients [kN-s/m]
[kN-s/m]
1
Damping Coefficients [kN-s/m]
Cxx = Cyy,  = 0.25
Cxx = Cyy,  = 0.55
0.8
Equivalent Viscous Damping, Ceq
Cxx = Cyy, = 0.25
0.7
1200
Cxx = Cyy, = 0.55
Equivalent
Viscous
Damping,
0.6
Increasing
loss
factor
() Ceq
Cxx = Cyy, = 0.25
Increasing
lossloss
factor
(  =(Cyy,
Cxx
0.5
Increasing
factor
Pr = 2.4 = 0.55
Equivalent Viscous Damping, Ceq
Cxx = Cyy,  = 0.25
0.4
Cxx = Cyy,  = 0.55
Equivalent Viscous Damping,0.3
Ceq
0.80.8
0.8
0.70.7
0.7
111
600 rpm
0.9
Pr = 1.7
0.90.9
0.9
0.50.5
0.5
1
1200
rpm
1200
rpm
20
20
20 40
40
40
40 60
60
60
6080
80
80
80100
120
100
100
100
Frequency
[Hz]
Frequency
[Hz]
Frequency
[Hz]
Frequency
[Hz]
0.1
0
0
0
20
40
60
80
100
0
120
20
40
60
80
100
Frequency [Hz]
HBS direct damping
Frequency [Hz] (Csxx) decreases with excitation
frequency. Loss factor coefficient () represents physically
seal structural (hysteresis) damping
GT2009-59072 Hybrid Brush Seal Force Coefficients
Conclusions
•Prior to shaft rotation, seal pads lift-off due to hydrostatic
effect from pressurization. Break-away torque is 90% less
when seal is pressurized. Rotor speed has negligible effect on
HBS drag torque (power loss) and leakage.
•A structural loss factor (γ) and a dry friction coefficient()
effectively characterize the energy dissipation mechanism of
the HBS.
•HBS direct stiffness (Ksxx = Ksyy) decreases minimally with
rotor increasing rotor speed for Pr = 1.7 and 2.4.
• HBS cross-coupled stiffness (Ksxy = -Ksyx) is one order of
magnitude smaller than direct stiffnesses.
•HBS direct viscous damping coefficients decrease with
increasing excitation frequency.
GT2009-59072 Hybrid Brush Seal Force Coefficients
Acknowledgments
Thanks to
• Siemens Power Generation,
• Advanced Technologies Group (Mr. John Justak)
www.advancedtg.com
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GT2009-59072 Hybrid Brush Seal Force Coefficients
HIGH TEMPERATURE SEAL FACILITY
Properties
Specific gas constant, R
Supply pressure, Ps
Inlet temperature, T
Exhaust pressure, Pe
Ambient temperature
Magnitude
287 J/kg-K
101-760 kPa
298-573 K
101 kPa
298 K
V oltage
240 V
90 V
H eater
M otor
Flow in
(supply pressure)
M axim um
P ow er
12 kW
850 W
O utput
300°C
3,000 rpm
1
3
6
3
Flow out
(ambient pressure)
Pe =101 kPa
8
2
7
4
0
10
20
cm
1
2
3
4
Hot air inlet
Pressurized cylinder & shaft
Radial support bearings
Disc and test seal location
5
6
7
8
Optical displacement sensor
Centering mechanism
Coupling and quill shaft
Electric drive motor
2009 STLE Annual Meeting, May 2009
GT2009-59072 Hybrid Brush Seal Force Coefficients
Compare Leakage from Three Seals
40
m T
35
Ps D
 
30
25
20
15
10
5
•Air temperature and rotor
speed affect little the flow
factor. Show comparisons
at max conditions
40
Flow Factor [kg-K 0.5/(MPa-m-s)]
Flow Factor [kg-K 0.5/(MPa-m-s)]
Flow factor
0
35
30
25
• HBS has lower flow factor
than both the labyrinth seal
(38%) and the brush seal
(61%)
20
15
10
Labyrinth Seal
Brush Seal
5
Hybrid Brush Seal
0
1.0
1.5
1.02.0
1.52.5
2.03.0
2.53.5
3.04.0
Pressure Ratio Pressure
[Ps/Pe]
Ratio [P /P ]
s
e
3.5
• The brush seal and HBS
begin with same clearance.
HBS
4.0 is more effective in
reducing leakage
Max. air temperature (300ºC) & rotor speed (3 krpm)
2009 STLE Annual Meeting, May 2009
GT2009-59072 Hybrid Brush Seal Force Coefficients
Backup slides
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Pad Lift Off upon Pressurization
Hybrid brush seal profile section
HP
Front plate
LP
Back
plate
Back plate
16.674 mm
Bristle pack
Cantilever
beam
Pad profile
0.254 mm
4.445 mm
7.750 mm
ROTOR
Ps
Pd
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Leakage (No Shaft Rotation)
Supply Pressure
= 5 to 30 psig
30.0
30.0
30.0
25.0
25.0
Mass Flow Rate [g/s]
Leakage
Mass
Flow Rate
Rate[g/s]
[g/s]
Mass Flow
[g/s]
25.0
20.0
20.0
20.0
SBS
15.0
15.0
15.0
HBS
10.0
10.0
10.0
5.0
5.0
5.0
0.0
0.0
0.0
1.0
1.0
1.0
1.5
1.5
1.5
2.0
2.5
2.0
2.5
2.0
2.5
Pressure
Ratio,
Pressure Ratio,Pr
Pr
Pressureratio,
Ratio,Pr
Pr
Pressure
3.0
3.03.0
3.5
3.5 3.5
Measured
HBS leakage
is ~ 36% less
than that for
a 1st
generation
SBS over the
test supply
pressure
range
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
Calculated Effective Clearance
Supply Pressure
= 5 to 30 psig
[mm]
Clearance
Effective
Clearance
[mm]
Effective
Clearance
[mm]
Effective
Clearance
[mm]
0.08
0.08
0.08
0.07
0.07
0.07
0.06
0.06
0.06
0.05
0.05
0.05
Effective
clearance
(CE) as if
one tooth
laby seal
SBS
0.04
0.04
0.04
HBS
0.03
0.03
0.03
0.02
0.02
0.02
0.01
0.01
0.01
0.00
0.00
1.0
1.0
1.0
.
1.5
1.5
1.5
2.5
2.0
2.0
2.5
2.0
2.5
PrPr
Ratio,
Pressure
PressureRatio,
Ratio,Pr
Pressure
Pressure
ratio,
Pr
3.0
3.0
3.0
3.5
3.5
3.5
cE 
m
(T  273.15)
Pu  D 
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Leakage vs. Pressure Drop
30.0
Static Condition
600 RPM
1300 RPM
[g/s]
Leakage
Mass Flow Rate
[g/s]
25.0
20.0
15.0
10.0
5.0
0.0
1.0
1.5
2.0
2.5
3.0
3.5
Supply Pressure
= 5 to 30 psig
Seal leakage is
proportional to
pressure ratio
(discharge/exit
). Little
dependency on
rotor speed.
Pressure Ratio, Pr
Pressure ratio, Pr
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Break-Away Torque vs. Pressure Ratio
Seal Drag
Torque [N-m]
[N-m]
Torque
HBS Drag
10.0
Break-away Torque
10.0
8.0
As pressure
increases from Pr =
1.0 to 1.7, the
break-away torque
(i.e. no rotation)
Break-away Torque
8.0
6.0
6.0
4.0
2.0
drops by ~ 75%
4.0
2.0
0.0
1
1.5
2
2.5
3
Pressure Ratio, Pr
Pressure
ratio, Pr
0.0
Pads
lift-off prior to shaft rotation due to the generation of a
1
1.5
2
2.5
3
hydrostatic gas film as the pressure difference across the
Pressure Ratio, Pr
seal increases
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Power Loss vs. Speed & Feed Pressure
HBS Power Loss [W]
Loss
Power
HBSHBS
Power Loss
[W] [W]
600
600
600
HBS Power Loss [W]
500
500
500
Pr = 1.0 (No external
Pr = 1.0 (No external pressurization)
pressurization)
400
400
400
300
300
300
Pr = 1.7
200
200
200
Pr = 1.7
100
100
100
00 0
00 0
Pr = 2.4
Pr = 2.4
500
1000
500
1000
500
1000
Rotational
Speed
[RPM]
Rotational
Speed
[RPM]
Rotational
Speed
[RPM]
Rotor Speed [RPM]
ΔP +
1500
1500
1500
With external
pressurization
(Pr = 1.0 to
1.7), HBS
Power losses
decrease by ~
90% over test
rotor speed
range
Pads lift-off due to the generation of hydrodynamic gas-film eliminating
contact forces at the rotor/pads interface
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
Dynamic Load Tests (no shaft rotation)
FFext
ext xx
KKs s
s 
s s s 
KKeqeq
FFext
ext
Meqeq
M
LL LLf f LLs s
CCeqeq
zz
44mmmm
f=
LLf =
2244
21mmmm
f=
LLf =
2221
2488mmmm
LL==24
xx
Equivalent Test
System
M eq x  K eq x  C eq x  Fext
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
GT2009-59072 Hybrid Brush Seal Force Coefficients
Parameter Identification (no shaft rotation)
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
x  xe
Z 
F
x
i t
F  F ext e
 ( K eq   M
W 
2
F
ext
eq
i t
)  i  C eq
d
x
t
E dis   C eq x
E dis   eq  K eq x
2
Harmonic force
& displacements
Impedance Function
Work External
2
 4 F x
Viscous Dissipation
DRY FRICTION
&
STRUCTURAL
DAMPING
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Structural Coefficients
Load = 63 N, frequency: 20-100 Hz (no shaft rotation)
Hybrid Brush Seal
Pressure ratio*
Stiffness [kN/m]
Dry Friction coefficient, μ
Loss Factor coefficient, γ
Pr = 1.0
93 (±5)
0.66
0.42
Pr = 1.7
130 (±6)
0.51
0.40
Pr = 2.4
141 (±7)
0.64
0.27
Pr = 3.0
141 (±7)
0.69
0.22
*:atmospheric discharge pressure
• HBS stiffness increases slightly as supply pressure
increases (~35% for pressure ratios: 1 to 3).
•Dry friction coefficient increases ~5 % due to increase
in contact forces between seal components
•Loss factor (structural damping) decreases due to
stiffening effect of increasing pressure differential
across seal
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
GT2009-59072 Hybrid Brush Seal Force Coefficients
R e(F
R e(F
/X
)/ [N
[N/X
/m
] ] /m ]
R e(F
/)X)
[N
m
RR
e(F
X)
R e(F
e(F
/X
/X/m
) /[N
)[N[N
/m] ]
]/ m
HBS Dynamic Stiffness vs. Frequency
(no shaft rotation)
Load = 63 N, frequency: 20-100Hz
400
200
R e(F /X ) [N /m ]
(F/X) [kN/m]
[kN/m]
ReRe(F/x)
300
100
0
TESTs
-100
Model
Pr=1.7
Pr
=2.4
PrPr=1.7
= 1.7
PrPr=3.0
= 2.4
Pr
=2.4
PrPr=3.0
= 3.0
-200
-300
-400
Test Data
PrPr=1.7
= 1.7
PrPr
= =2.4
2.4
Pr=1.7
PrPr
= =2.4
3.0
Pr=3.0
Pr=3.0
0
20
40
Model
2
2
reproduces
K eq Keq –MMeqeqω 
real part of
the
Model
impedance
Frequency [Hz]
under the
F reque ncy [Hz]
Frequency [Hz]
Frequency [Hz]
F reque ncy [Hz]given supply
Frequency [Hz]
pressure
conditions.
Frequency
60[Hz]
80
100
Frequency
[Hz]
Frequency [Hz]
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
120
6000
6000
GT2009-59072
Hybrid Brush Seal Force Coefficients
6000
HBS Equivalent Viscous Damping vs.
Frequency (no shaft rotation)
4000
4000
4000
2000
C eq 
Load = 63 N,2000
frequency 20-110Hz
2000
10000
0
Log(Ceq)
(Ceq), [N-s/m]
[N-s/m]
Log
0Test
TestData
Data 20
0
Pr =20
1.7
0
0
0
Pr =20
2.4
40
60
80
40
40
60
60
80
80
ΔP +
1000
100
20
40
60
80
Frequency, [Hz]
Frequency
[Hz]
100


4 F
 x
Equivalent
100
damping increases
100
slightly with
pressure
differential. Results
typical of a system
with dry-friction &
material damping
energy dissipation
100
Pr = 3.0
0
 eq K eq
120