GT2009-59072 Hybrid Brush Seal Force Coefficients
ROTORDYNAMIC FORCE COEFFICIENTS OF A HYBRID BRUSH SEAL:
MEASUREMENTS AND PREDICTIONS
Luis San Andres Jose Baker Mast-Childs Professor Project Engineer Texas A&M University KBR, Inc.
Adolfo DelgadoMechanical Engineer
GE Global Research Center
ASME GT2009-59175
Supported by Siemens Power Generation
accepted for journal publication
ASME Turbo Expo 2009: Power for Land, Sea, and Air
GT2009-59072 Hybrid Brush Seal Force Coefficients
Justification
Improved Brush Seal Technology Offers:Higher engine performance with less parasitic
leakageImproved engine stability and reduced engine
vibrationLower operating and maintenance costs
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
GT2009-59072 Hybrid Brush Seal Force Coefficients
Brush seals vs. Labyrinth Seals
•Handle large amplitudes of vibration
•Less axial space
•Reduced secondary flow leakage (90%)
Advantages
Disadvantages
•Pressure differential limitation
•Wear and local thermal distortion
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
Hybrid Brush Seal (HBS) Advantages
• All the advantages of 1st generation SBS
• Reduced leakage (~36%) over 1st
generation shoed brush seal
• Pads connected via EDM-webs, no
spot welds between pads and bristles
• Higher axial stiffness, prevents pad
motions at high pressure differentials
GT2009-59072 Hybrid Brush Seal Force Coefficients
LITERATURE REVIEW: Hybrid Brush Seals
• Justak introduces a film riding seal
with hydrodynamic pad action. • Delgado and San Andrès measure leakage and structural characteristics of a shoed-brush seal.• San Andrès et al. 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 compare leakage performance of three seals at high temperature
(U.S. Patent 7,182,345)
(Sealing Technology, 2005)
(ASME GT2008-50532 )
(2009 STLE Meeting)
•Chupp et al. (2006): comprehensive review on sealing technology, including brush seals and shoed brush seals.
GT2009-59072 Hybrid Brush Seal Force Coefficients
Structural parametersKshaft= 243 lbf/in (42.5 kN/m)Ms+d= 9.8 lb (4.45 kg)
: 0.01 % (damping ratio)
Installation:6.550” diameter brush seal Max. air Pressure: 60 psig Shaker (20 lb max)
10 20 30 40 50 60 70 80 90 100
cm
Supply pressure inlet
Eddy current sensosrs
Pressure Vessel
Flexible coupling
Quill shaft
Rotor StingerElectromagneticShaker
DC Motor
Supporting springs
Rollerbearing assembly
Eddy current sensor
Spring
Ball bearing
Shaft
Disk
High pressure air
Flow
Flow Flexible coupling to motor
Hybrid brush sealDetail of brush seal test rig
Experimental Facility
Disc
Ps Pe
Seal
Flow
GT2009-59072 Hybrid Brush Seal Force Coefficients
Test Hybrid Brush Seal (HBS)
High Pressure Side Low Pressure Side
Bristle Bed
Pad or shoe
Back Plate
Spring Lever Mechanism
* Close-up courtesy of Advanced Technologies Group, Inc.
Physical Properties SI unit English Unit Rotor diameter, Dj 167.1 mm 6.580 in
Brush seal (pads) inner diameter, Dsi 166.4 mm 6.550 in Brush seal (retainer) outer diameter, Do 183.1 mm 7.210 in
Brush seal width, Bw 8.53 mm 0.336 in Radial Interference between rotor and seal, Ri 0.381 mm 0.015 in
Number of pads 20 Width of pads 7.23 mm 0.331 in
Bristle lay angle, α 45 deg. - Bristle modulus of elasticity, E 22.48x105 bar 32.6x106psi Bristle density (circumference) 850 bristle/cm 2200 bristle/ in
Courtesy of Advanced Technologies Group®
Disc
Ps Pe
Seal
Flow
GT2009-59072 Hybrid Brush Seal Force Coefficients
Identification of Rotordynamic Force Coefficients
iy
ixx
yyyx
xyxx
yyyx
xyxx
yyyx
xyxx
F
FF
y
x
CC
CC
y
x
KK
KK
y
x
MM
MM
0
Eddy current sensors
Y
X
Ω
Electromagnetic Shaker
Load Cell
Stinger
Disk
HBS
Kxx, Cxx
Kxy, Cxy
Kyx, Cyx
Kyy, Cyy
X
Y
For rotor centered operation:
GT2009-59072 Hybrid Brush Seal Force Coefficients
xxyxx FyZxZ
0 yZxZ yyyx
yxiCMKZ ,2 ,
Identification of HBS rotordynamic force Coefficients
Identification at excitation frequency (ω) ≠ rotor speed (Ω)
System Impedances
Impedance Function
yyxx ZZ and yxxy ZZ
GT2009-59072 Hybrid Brush Seal Force Coefficients
Effect of rotor speed on rotor-HBS natural frequency
-0.1
-0.075
-0.05
-0.025
0
0.025
0.05
0.075
0.1
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Axial Location, [m]
Sh
aft
Ra
diu
s,
[m]
-0.1
-0.075
-0.05
-0.025
0
0.025
0.05
0.075
0.1
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Axial Location, [m]
Sh
aft
Ra
diu
s, [
m]
Hybrid Brush Seal location
Axial Location, [m]
Roller bearing support
Disk
Shaft
Location of external force
Location of displacement measurements
Sh
aft
Ra
diu
s, [m
]
Gyroscopic effects negligible
for test rotor speeds
(600 and 1,200 rpm [20 Hz])
RotorSpeed [RPM]
1st Backward Nat. Frequency, [Hz]
1st Forward Nat. Frequency, [Hz]
2nd Forward Nat. Frequency, [Hz]
3rd Forward Nat. Frequency, [Hz]
0 30.5 30.5 146 1351
600 29.7 31.4 154 1351
1200 28.8 32.2 163 1351
Axial Location, z [m]
Sha
ft R
adiu
s [m
]
GT2009-59072 Hybrid Brush Seal Force Coefficients
40 40 120 200 280 360 4400
250
500
750
1000
Frequency [Hz]
X -
Dis
plac
emen
t [um
]
40 40 120 200 280 360 4400
250
500
750
1000
Frequency [Hz]
Y -
Dis
plac
emen
t [um
]
32 Hz Due to excitation
Synchronous with speed (1X)
32 Hz
Due to excitation
22 N
22 N
Synchronous with speed (1X)
Cross coupling effects under rotation
For load along X direction,
rotor (X) motions
>>> cross (Y) motions
1X motions always small compared to
excitation
Load=22 N600 rpm
Frequency [Hz]
X-d
ispl
acem
ent
[m
]Y
-dis
plac
emen
t [m
]
Frequency [Hz]
X
Y
GT2009-59072 Hybrid Brush Seal Force Coefficients
0 20 40 60 80 1001 106
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(Z
xx1)
[N/m
]
0 20 40 60 80 1001 106
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(Z
xx1)
[N/m
]
0 20 40 60 80 1001 106
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(Z
xx1)
[N/m
]
0 20 40 60 80 1001 106
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(Z
xx1)
[N/m
]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m]
0 20 40 60 80 1001 106
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(Z
xx1) [N
/m
]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(
Zxx1
) [N
/m]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(
Zxx1
) [N
/m]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re(
Zxx1
) [N
/m]
Test Data 600 rpm, Pr = 1.7 1200 rpm, Pr = 1.7 600 rpm, Pr = 2.4 1200 rpm, Pr = 2.4
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m
]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m]
0 20 40 60 80 1001 10
6
5 105
0
5 105
Test DataModel
Frequency [Hz]
Re
(Z
xx1
) [N
/m]
Model
Kxx - 2Mxx
Dynamic Stiffness vs. FrequencyLoad = 22 N, frequency 25-80Hz )( 22 yx
xFZ x
xx
Model reproduces
the measured real part of
impedance.Little effect of
pressurization
2xx xxK M
Model
TESTs
Frequency [Hz]
Re
(Zxx
) [k
N/m
]
GT2009-59072 Hybrid Brush Seal Force Coefficients
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)
Frequency [Hz]
Re(
Zxy
) [N
/m]
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)
Frequency [Hz]
Re(
Zxy
) [N
/m]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X) [N
/m
]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X
) [N
/m
]
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re
(F
/X
) [N
/m
]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X) [N
/m
]
Model
Test Data
Pr = 1.7, Zxy =- Zyx
1200 rpm
600 rpm
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)
Frequency [Hz]
Re
(Zxy
) [N
/m]
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)
Frequency [Hz]
Re(
Zxy
) [N
/m]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X) [N
/m]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X
) [N
/m
]
0 20 40 60 804 104
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re
(F
/X
) [N
/m
]
0 20 40 60 804 10
4
2 104
0
2 104
4 104
Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)
Frequency [Hz]
Re(F
/X) [N
/m]
Model
Test Data
1200 rpm
600 rpm
Pr = 2.4, Zxy =- Zyx
Cross-coupled Stiffness vs. FrequencyLoad = 22 N, frequency 20-80Hz
•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
x
yZZZ xxyxxy
Pressure ratio Pr=1.7 Pr=2.4
Rotor Speed [rpm], Ω600 1200 600 1200
Stiffness [kN/m], Kxy 8.8 15 2.7 6.6
Mass [kg.], Mxy 0 0 0 0
GT2009-59072 Hybrid Brush Seal Force Coefficients
Equivalent Viscous Damping (Cxx~Ceq) vs. Frequency
Damping decreases with frequency, with
little effect of supply
pressure. Minimum value at test system
natural frequency (~32
Hz)
Pr=1.7
600 rpm
Pr=2.4
1200 rpm
Supply Pressure/Exhaust Pressure
GT2009-59072 Hybrid Brush Seal Force Coefficients
Force coefficiensts: system & sealLoad = 22 N, frequency 25-80Hz
No rotationTests with rotor spinning
Pressure ratio Pr = 1.0 Pr=1.7 Pr=2.4
Rotor Speed [rpm], Ω 0 600 1200 600 1200
Stiffness [kN/m], Kxx120
108 98 130 124
Mass [kg.], Mxx2.11 2.62 2.54 2.43 2.39
R2 (correlation factor)Dynamic stiffness (Kxx – Mxxω
2)0.97 0.98 0.98 0.98 0.98
HBS stiffness[kN/m], Ks 93 103 89 135 128
HBS Dry Friction coefficient, μ
0.660.39 0.36 0.37 0.38
HBS Loss Factor coefficient, 0.42 0.29 0.26 0.33 0.34
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS predicted stiffness vs. frequencyFrequency 25-100 Hz
Predicted HBS stiffness (Ksxx)
drops slightly in range from 20-
100 Hz.Tests show nearly
constant Ksxx
Pressure (Pr = Ps/Pd) has negligible effect on seal direct
stiffness, Ksxx
60
70
80
90
100
110
120
130
140
0 20 40 60 80 100 120
Frequency [Hz]
Stif
fnes
s C
oeffi
cien
ts [k
N/m
]
60
70
80
90
100
110
120
130
140
0 20 40 60 80 100 120
600 rpm
1,200 rpm
60
70
80
90
100
110
120
130
140
0 20 40 60 80 100 120
Ksxx = Ksyy, Pr = 1.0Ksxx = Ksyy, Pr = 1.7Ksxx = Ksyy, Pr = 2.4Ksxx = Ksyy, Pr = 1.0
Ksxx = Ksyy, Pr = 1.7Ksxx = Ksyy, Pr = 2.4
HBS Equivalent Stiffness, Ks HBS Equivalent Stiffness, Ks
HBS Measured Stiffness, Ks
60
70
80
90
100
110
120
130
140
0 20 40 60 80 100 120
Ksxx = Ksyy, Pr = 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
Ksxx = Ksyy, Pr = 1.0
Ksxx = Ksyy, Pr = 1.7
Ksxx = Ksyy, Pr = 2.4
HBS Equivalent Stiffness, Ks HBS Equivalent Stiffness, Ks
HBS Measured Stiffness, Ks
Code: XLTPGASBEAR®
Frequency [Hz]
Stif
fnes
s C
oeff
icie
nts
[kN
/m]
ASME GT2004-53614
GT2009-59072 Hybrid Brush Seal Force Coefficients
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Frequency [Hz]
Dam
ping
Coe
ffici
ents
[kN
-s/m
]
1200 rpm
Increasing loss factor (
HBS viscous damping coeff. vs. frequencyFrequency 25-100 Hz
HBS direct damping (Csxx) decreases with excitation frequency. Loss factor coefficient () represents physically seal structural (hysteresis) damping
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Cxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, CeqCxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, Ceq
1200 rpm
Increasing loss factor (
Pr = 2.4
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Cxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, CeqCxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, Ceq
1200 rpm
Increasing loss factor (
Pr = 1.7
1,200 rpm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
1200 rpm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
1200 rpm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Frequency [Hz]
Dam
ping
Coe
ffici
ents
[kN
-s/m
]
1200 rpm
Increasing loss factor (
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Cxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, CeqCxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, Ceq
1200 rpm
Increasing loss factor (
Pr = 1.7
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Cxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, CeqCxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, Ceq
1200 rpm
Increasing loss factor (
Pr = 2.4
600 rpm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Increasing loss factor () Increasing loss factor ()
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
Thanks to
• Siemens Power Generation,
• Advanced Technologies Group (Mr. John Justak) www.advancedtg.com
Acknowledgments
Questions ?
Learn more at http://phn.tamu.edu/TRIBGroup
GT2009-59072 Hybrid Brush Seal Force Coefficients
HIGH TEMPERATURE SEAL FACILITY
1 Hot air inlet 5 Optical displacement sensor2 Pressurized cylinder & shaft 6 Centering mechanism
3 Radial support bearings 7 Coupling and quill shaft4 Disc and test seal location 8 Electric drive motor
8
3
2
3
4
6
1
7
Flow in (supply pressure)
Flow out (ambient pressure) Pe =101 kPa
0 10 20
cm
Voltage Power OutputHeater 240 V 12 kW 300°CMotor 90 V 850 W 3,000 rpm
MaximumProperties Magnitude
Specific gas constant, R 287 J/kg-K
Supply pressure, Ps 101-760 kPa
Inlet temperature, T 298-573 K
Exhaust pressure, Pe 101 kPa
Ambient temperature 298 K
2009 STLE Annual Meeting, May 2009
GT2009-59072 Hybrid Brush Seal Force Coefficients
0
5
10
15
20
25
30
35
40
1.0 1.5 2.0 2.5 3.0 3.5 4.0
Pressure Ratio [Ps/Pe]
Flo
w F
ac
tor
[kg
-K0
.5/(
MP
a-m
-s)]
Max. air temperature (300ºC) & rotor speed (3 krpm)
Compare Leakage from Three Seals
0
5
10
15
20
25
30
35
40
1.0 1.5 2.0 2.5 3.0 3.5 4.00
5
10
15
20
25
30
35
40
1.0 1.5 2.0 2.5 3.0 3.5 4.0
Labyrinth Seal
Brush Seal
Hybrid Brush Seal
•Air temperature and rotor speed affect little the flow
factor. Show comparisons at max conditions
• HBS has lower flow factor than both the labyrinth seal
(38%) and the brush seal (61%)
• The brush seal and HBS begin with same clearance.
HBS is more effective in reducing leakage
Flow factor
DP
Tm
s
2009 STLE Annual Meeting, May 2009
GT2009-59072 Hybrid Brush Seal Force Coefficients
Backup slides
GT2009-59072 Hybrid Brush Seal Force Coefficients
HP LP
ROTOR
Pad profile
Backplate
Cantilever beam
4.445 mm
0.254 mm
7.750 mm
Front plate
Bristle pack
Back plate 16.674 mm
Hybrid brush seal profile section
HBS Pad Lift Off upon Pressurization
Ps
Pd
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
0.0
5.0
10.0
15.0
20.0
25.0
30.0
1.0 1.5 2.0 2.5 3.0 3.5Pressure Ratio, Pr
Mas
s F
low
Rat
e [g
/s]
0.0
5.0
10.0
15.0
20.0
25.0
30.0
1.0 1.5 2.0 2.5 3.0 3.50.0
5.0
10.0
15.0
20.0
25.0
30.0
1.0 1.5 2.0 2.5 3.0 3.5
HBS Leakage (No Shaft Rotation)
Measured HBS leakage is ~ 36% less than that for
a 1st generation
SBS over the test supply
pressure range
SBS
HBS
Supply Pressure = 5 to 30 psig
Pressure ratio, Pr
Lea
kag
e [g
/s]
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
1.0 1.5 2.0 2.5 3.0 3.5Pressure Ratio, Pr
Effe
ctiv
e C
lear
ance
[mm
]
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
1.0 1.5 2.0 2.5 3.0 3.50.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
1.0 1.5 2.0 2.5 3.0 3.5
Calculated Effective Clearance
Effective clearance
(CE) as if one tooth laby seal
.
( 273.15)E
u
m Tc
P D
SBS
HBS
Supply Pressure = 5 to 30 psig
Pressure ratio, Pr
Cle
aran
ce [m
m]
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
Seal leakage is proportional to pressure ratio
(discharge/exit). Little
dependency on rotor speed.
0.0
5.0
10.0
15.0
20.0
25.0
30.0
1.0 1.5 2.0 2.5 3.0 3.5
Pressure Ratio, Pr
Mas
s F
low
Rat
e [g
/s]
Static Condition
600 RPM
1300 RPM
HBS Leakage vs. Pressure Drop
Pressure ratio, Pr
Leak
age
[g/s
]
Supply Pressure = 5 to 30 psig
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
0.0
2.0
4.0
6.0
8.0
10.0
1 1.5 2 2.5 3
Pressure Ratio, Pr
Sea
l Dra
g T
orq
ue
[N
-m]
Break-away Torque
HBS Break-Away Torque vs. Pressure Ratio
As pressure increases from Pr =
1.0 to 1.7, the break-away torque
(i.e. no rotation)
drops by ~ 75%
Pads lift-off prior to shaft rotation due to the generation of a hydrostatic gas film as the pressure difference across the seal increases
Pressure ratio, Pr
HB
S D
rag
To
rqu
e [
N-m
]
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
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
HBS Power Loss vs. Speed & Feed Pressure
0
100
200
300
400
500
600
0 500 1000 1500Rotational Speed [RPM]
HB
S P
ow
er
Lo
ss [
W]
Pr = 1.7 Pr = 2.4
Pr = 1.0 (No external pressurization)
0
100
200
300
400
500
600
0 500 1000 1500
0
100
200
300
400
500
600
0 500 1000 1500
Pr = 1.0 (No external pressurization)
Pr = 1.7
Pr = 2.4 ΔP +
Rotor Speed [RPM]
HB
S P
ower
Los
s [W
]
ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505
GT2009-59072 Hybrid Brush Seal Force Coefficients
Fext x
L
Ks
ss
z
Ls Lf
Fext
Lf =244 mm Lf =221 mm L= 248 mm
Dynamic Load Tests (no shaft rotation)
exteqeqeq FxCxKxM
Equivalent Test System
Meq
Keq
Ceq
Fext
x Lf =244 mm Lf =221 mm L= 248 mm
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
GT2009-59072 Hybrid Brush Seal Force Coefficients
Harmonic force & displacements
Impedance Function
Work External
Viscous Dissipation
tixex tiexteFF
eqeqeq CiMKx
FZ )( 2
extFW x dt
xFxKE eqeqdis 42
2xCE eqdis
Parameter Identification (no shaft rotation)
DRY FRICTION &
STRUCTURAL DAMPING
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
GT2009-59072 Hybrid Brush Seal Force Coefficients
HBS Structural CoefficientsLoad = 63 N, frequency: 20-100 Hz (no shaft rotation)
Hybrid Brush Seal
Pressure ratio* Pr = 1.0 Pr = 1.7 Pr = 2.4 Pr = 3.0 Stiffness [kN/m] 93 (±5) 130 (±6) 141 (±7) 141 (±7) Dry Friction coefficient, μ 0.66 0.51 0.64 0.69 Loss Factor coefficient, γ 0.42 0.40 0.27 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
Frequency [Hz]
Re(
F/X
) [N
/m]
Frequency [Hz]
Re(
F/X
) [N
/m]
Frequency [Hz]
Re(
F/X
) [N
/m]
Frequency [Hz]
Re
(F/X
) [k
N/m
]
0 20 40 60 80 100 120
-400
-300
-200
-100
0
100
200
300
400
Keq – Meqω2
Pr=1.7Pr=1.7
Frequency [Hz]
Re(
F/X
) [N
/m]
Pr=1.7Pr=1.7
Frequency [Hz]
Re(
F/X
) [N
/m]
Pr=3.0Pr=3.0
Frequency [Hz]
Re(
F/X
) [N
/m]
Pr=3.0Pr=3.0
Frequency [Hz]
Re(
F/X
) [N
/m]
Pr=2.4Pr=2.4
Frequency [Hz]
Re(F/X
) [N/m]
Pr=2.4Pr=2.4
Frequency [Hz]
Re(F
/X) [
N/m]
Model Test Data Pr = 1.7
Pr = 2.4
Pr = 3.0
Pr = 1.7
Pr = 2.4
Pr = 3.0
HBS Dynamic Stiffness vs. Frequency (no shaft rotation)
ModelTESTs
Load = 63 N, frequency: 20-100Hz
Model reproduces real part of
the impedance
under the given supply
pressure conditions.
Frequency [Hz]
Re
(F/x
) [k
N/m
]
2eqeq MK
ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655
GT2009-59072 Hybrid Brush Seal Force Coefficients
Load = 63 N, frequency 20-110Hz
0 20 40 60 80 100 120 100
1000
10000
Frequency, [Hz]
Log
(Ceq
), [N
-s/m
]
0 20 40 60 80 1000
2000
4000
6000
8000
Pr = 1.7
0 20 40 60 80 1000
2000
4000
6000
8000
Pr = 2.4
0 20 40 60 80 1000
2000
4000
6000
8000
Pr = 3.0
Test Data Test Data
ΔP +
Equivalent damping increases
slightly with pressure
differential. Results typical of a system with dry-friction & material damping
energy dissipation
HBS Equivalent Viscous Damping vs. Frequency (no shaft rotation)
x
FKC eqeq
eq
4
Frequency [Hz]
Log
(Ceq
) [N
-s/m
]
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